General Notes:  (mostly derived from the Norton Anthology of English Literature, 5th Ed. Vol. 2 pp. 59-60:  the introduction to this work)
This was written in response to the Swedish theologian and visionary, Emanuel Swedenborg, who wrote prophetic books that at first were admired by Blake.  Later, though, it seems that Blake 'saw through' the rhetoric and recognized that Swedenborg actually says nothing new:  he was a "conventional Angel in the disguise of a radical Devil."  (60).  (see plates 21-22 below)  Blake, on the other hand, saw himself as the real thing.  
Blake emphasizes the "contrarieties" which he had started with his description of the 'contrary state' of being, Experience, (contrasted with Innocence, you see); he emphasizes that "without contraries is no progression;" though much of the "marriage" is ironic, this seems to be in earnest, and is a recurring theme in his other poems as well.  Norton explains that "the real Good, as distinguished from the merely ironic Good, is not instinctual abandon but a "marriage," or union of the contraries, of desire and restraint, energy and reason, the promptings of Hell and the denials of Heaven. . .'the Prolific' and 'the Devouring'.  "  (59)  Though Blake says that Good should be comprised of these contrarieties, they should be in a state of tension; to reconcile them instead "seeks to destroy existence."  It is suggested that that's exactly what the Church has been trying to do.
At first, Blake seems to be playing the Devil:  that is, acting as a kind of Devil's advocate.  Norton suggests that this is "designed to startle the reader into recognizing the inadequacy  of conventional moral categories and stock responses.  
Blake, along with  Wordsworth, Coleridge, and Southey, expected that the French Revolution, still young and idealized at the time of composition (the early 1790s), preceded of course by the American Revolution, were signs of the coming Apocalypse, and that the Second Coming of Christ was coming real soon.  So this poem suggests this idea.
Unless there is specific credit given, the notes below are derived from the Blake and from the mind of Chris O'Brien.  For richer or for poorer.

Plate 2:  The Argument (in verse)  (Show the passage)
This is the only part of this work to be written in a kind of extra-blank verse.  At least, there are short lines.  It reads as being pretty modern, though it's before its time.  The meter is so irregular that I can't tell if we, the readers, in order to form a more perfect scansion, ought to 'compensate' or DIO (ourselves), or if it's just whacky.  Maybe Blake was just working directly from inspiration and didn't want to bust the original transcription.  

Anyhow, (notice I didn't suggest that Blake was a hack that time?  I'm getting better!)  I must report that Norton reports an interpretation of this part:  the history of Biblical history up to the "present" time.  Verse 2 is the time after the fall of man; verse 3 is the birth of Christ; verse 4 is the time when 'Christianity was perverted into an institutional religion'; verse 5 is the time of the French Revolution--"now".  (60)  The first and sixth verses are bookends again.  These bookends suggest an affinity to the structure of classical music; pieces in ternary (ABA) structure or the rondo form with a recurring theme, or the older ritornello, are sometimes like that.
The line "the burdend air" suggest the haze of air pollution.  
"red clay" (mentioned in line 13) is the literal meaning of Adam; Norton suggests that the reference there is to the New Adam--Jesus.
Rintrah is sometimes taken to be Blake himself, similar to the figures of Elijah or John the Baptist, who were "crying in the wilderness" in the Bible; the ironic passages that follow are his sermon, but they take the form of a kind of cautionary "reverse psychology" treatment.  (Norton 60-61)

Plate 3:  more argument, in prose.  (Show the passage)
This is the 'establishing shot' of the "marriage."  
This is interesting enough to quote from Norton.  "Swedenborg (1688-1772) had predicted, on the basis of his visions, that the Last Judgment and the coming of the Kingdom of Heaven would occur in 1757.  This was precisely the year of Blake's birth.  Now, in 1790, Blake is thirty-three, the age at which Christ had been resurrected from the tomb; appropriately, Blake rises from the tomb of his past life in his new role as imaginative artist who will redeem his age.  But, Blake ironically comments, the works he will engrave in his resurrection will constitute the Eternal Hell, the contrary inevitably brought into simultaneous being by Swedenborg's limited New Heaven."  (Norton, 61)
This is a response to places in the Bible.  Suffice it to say that Blake is interpreting the Bible and guessing that it is talking about Adam recovering his lost paradise.  The "red man" mentioned in the Bible, see Blake's reference, is the spirit of the French Revolution coming to England.  This spirit is to Blake a sign of the coming Apocalypse, redemption, and the recovery of Paradise.  (Norton 61 and CJO)
Notice the emphasis on contraries.  These are crucial to Blake's way of thinking, just as the Cross would not work if it only went in one direction.  It's the convergence that gets things done.  


Plate 4:  The Voice of the Devil, part 1:  errors caused by sacred codes.  (Show the passage)
Here's Blake quoting the Devil for God's purposes:  a deliberate reversal.  Blake didn't support the Devil, far from it, but he is against the "perversion" of the organized church.  The Bibles or sacred codes, related to the organization and codifying of the Church, is charged with teaching a false dichotomy of the Body (related to evil and energy and evil) and the Soul (related to passivity and reason and good); there is in fact, the Devil says, no such separation.  The Devil says that the church teaches damnation for acting upon one's energies, but then says that the Body is just part of the Soul that is perceived by the five senses.  The Devil says that energy is the only life, and that Reason is peripheral.  Read it yourself if you don't believe me.
Here are some truths, in response, about Blake's methods in this Plate.

1. Blake speaks as the Devil
2. Blake speaks against the teachings of the Church
3. His principles do actually go against the church teachings.
4. Nevertheless, the propositions do read as very reasonable.  
5. That's because, for one thing, it makes sense; 
6. For another, it is explained in a "logical," methodical way.
7. So Christians should support it, though the Devil is speaking against Logic, he uses Logic to make his point..
8. So it seems like the Christians can learn something holy from it, 
9. Meaning that Blake is speaking in support of the true spirit of Christianity, which doesn't make sense, because
10. Blake is speaking as the Devil.  

This vicious circle makes it hard to grasp the real attitude Blake is projecting here.   But it is fun.
Finally, it seems that this "devil" is really a reasonable--that is, a nice and non-evil--guy, misunderstood because of the Church's mis-teachings, and actually is quite moral if we the readers can get away from the moral codes taught by the organized church.

Plates 5-6:  principles; Milton's "Paradise Lost"  (Show the passage)

Blake regarded Milton as a poet-prophet.  He makes specific charges and descriptions that, to understand fully, you need to know your Milton and your Bible real well.  I don't.  Just read what he says, smile, nod noncommitally, and go on.  I am just not in the intended audience that Blake intended to be the readers of this passage, I guess.  Notable is the Devil's charge that Milton was, as a True Poet, a member of the Devil's party, but he didn't know it; that's why he can't speak freely about the Angels or God.

Plate 6, part 2-Plate 7, top:  A Memorable Fancy (1)  (Show the passage)
These "Memorable Fancies" are parodies of the "memorable relations" in Swedenborg's writings, about "literal-minded visions of the eternal world" (Norton 63).
Here Blake reinforces the ideas that the Church and the Angels misunderstand the Devil and Hell.  The Devil's "genius" is the Angels' "torment and insanity."  The following 'proverbs' are the sayings of these geniuses in Hell, quoted to show the national character of Hell by the sayings used there.  
Norton tells me--and now you--that the "mighty Devil" in paragraph 2 is Blake, "as he sees himself reflected in the shiny plate on which he is etching this very passage with "corroding fires"--i.e. acid.  (63)


Plate 7, bottom-10:  Proverbs of Hell  (Show the passage)
Some of these are reverses of common proverbs.  Some are really hellish-sounding; vicious.  Many seem sensible enough.  The motivation for many is selfish gain, "looking out for Number One."  General social commentary with a sardonic twist.  Actually some of these read in the style of Ben Franklin, who was an elder contemporary of Blake's, who wrote lots of wise sayings in Poor Richard's Almanack, and other places.
Note the *possible* reference, or convergent creativity, in the last line of Plate 10, and "Losing My Religion"'s line "Oh no I've said too much/I haven't said enough."  Similar in spirit.  More similar in fact to Coleridge's waffling on whether the end of "The Rime of the Ancient Mariner" has not enough moral, or too much.
This is good reading, and amusing.

Plate 11:  How men forgot that all deities reside in the human breast  (Show the passage)
Blake claims that early animism treated everything as if it had a God inside (cf. "Colors of the Wind"); then they pretended that cities and countries had 'mental deities' too; then it was codified and used by the early Priesthood to rook and enslave the common people.  They conducted ceremonies according to poetic tales, then forgot the origin of the tales and supposed that the Gods had ordered them.  Simple.  Maybe true.

Plates 12-13:  A Memorable Fancy:  Dinner with Isaiah and Ezekiel  (Show the passage)
The Devil states that he's debunked the prophets by allowing them to "confess" their sham--they had not seen God but only played a mind game and called it the voice of God.  Firm "perswasions" are believed by all poets to be true, and that such conviction of the heart used to be the "faith that moved mountains" but now many cannot be thus convinced anymore.  Ezekiel interprets the Old Testament to show that this kind of belief can really have power by showing how, by sharing a mindset, "all nations believe the Jews' code and worship the Jews' god, and what greater subjection can be?"  The rest of this escapes me and my interest.

Plate 14:  the tree of life burnt; etching allegory; the doors of perception  (Show the passage)

First, the Devil explains how, when the world ends, everything will appear infinite and holy, not by real cleansing of infinity, but instead by the cleansing of the senses, which Blake has said already to be limiting; the world will look new because of "an improvement of sensual enjoyment".  Perception must be expanded and cleansed; the "narrow chinks of his cavern" seem to suggest the five senses which are flawed and 'narrow"

Plate 15:  A Memorable Fancy:  A Printing house in Hell  (Show the passage)

According to dear Norton, this is simply an allegory for the procedure Blake uses to make his books:  the steps are designing, etching, printing, binding, and distribution.  (67)

Plate 16-17 top:  two classes of men  (Show the passage)

These are the Prolific and the Devourers; I think that maybe these are both present in everyone, actually, but for here Blake means two different kinds of people.  The Prolific are the Giants who formed the world in its sensual existence, and now seem to live in chains.  The chains are just the laws of the Church, (I think) and the Devourers make the chains.  The Devourers are seen to be cuning and weak.  Nevertheless, the Prolific need the Devourers in order to catch their excesses; without the contrary, they would not be prolific any more.  
Traditionally God the Father is seen as the creator of all, and the Devil is seen as the destroyer; this kind of twists that up.  
Blake says that these 2 kinds of men are enemies and should not get along, but oppose each other; the church, seeking to reconcile the two, seeks to destroy existence.  He adds that Jesus did not want to reconcile them; that tendency is a perversion.

Plate 17 bottom-20:  A Memorable Fancy:  the progress from the Manger to the Manager  (Show the passage)

This reads a bit like the nighmarish and evidently symbolical passages from the Revelations.  This appears more to be told from the point of view of Blake, not the Devil, or of one pretending to be the other; it's not too clear.  The focus seems to be on the correctness of the Angels and the Devils, and note the harper's tune:  "The man who never alters his opinion is like standing water, & breeds reptiles of the mind."  Whatever.  
Plates 21-22 top:  Swedenborg (Show the passage)

Getting specific in complaints against Swedenborg.  But it is in (surprise) plain English.  
Plate 22-24:  A Memorable Fancy:  How Jesus broke the ten commandments.  (Show the passage)

Almost there.  All the things the Devil mentions are Biblical.  But Blake may be forgetting the words of Jesus, "I do not come to ___ the law, but to fulfil it."  (I'll have to look that up later).  The ten commandments were from Moses's time, for people who didn't have the Redeemer yet.  The focus is in the line:  "I tell you, no virtue can exist without breaking these ten commandments.  Jesus was all virtue, and acted from impulse, not from rules."    A nice coda.  And the signal that it's the main point is that the angel becomes a devil.  Blake never seems to be against God and Jesus; instead, he's against the confinement of the senses and rules.  Anyway, I guess it shook some people up to read it.  Good.

This is the end of my notes on "The Marriage of Heaven and Hell;" next stop:  "The Book of Thel"