(Update: Recently the website containing the booklet has moved to http://www.mostimportantstory.net/. The whole booklet was available at a previous version of that website and a copy is archived here or if you prefer here is a montage. )
I initially only had four photocopied pages received after writing to the UK office of Samaritan's Purse. It was unclear from their letter whether this was the whole of the booklet. It looked like there are major parts of the story missing, so I guessed this was not all. The first attemp to obtain the original booklet were frustrating as despite being told by Samaritan's Purse that the booklet will be available in Christian bookshops the first Christian bookshop asked said they did not sell anything by the publisher "WorldServe Ministries" since they consider them to be a (quote ) "fringe group."
A websearch eventually found the whole booklet online available here from the website of "WorldServe Ministries." As it states at the bottom of http://www.mostimportantstory.
"The Greatest Gift of All" ISBN: 1 896658 32 6 Published by "WorldServe Ministries"
However the "WorldServe Ministries" website call the booklet "The most Important Story Ever Told."
As can be seen by comparing the photocopies and the full version - this is the same thing. Subsequently I wrote to the head office of Samaritan's Purse for clarification.
They anwered:
You are correct in your assumption that "The Most Important Story Ever Told" and "The Greatest Gift Of All" are basically one in the same. Samaritan's Purse has adopted this version for distribution with each shoebox gift as a tool for evangelism. (Full letter here)
The booklet is directly aimed at turning young children into Christians and comes complete with a "sinner's prayer" of conversion and a pledge card. See for yourself.