This is the original novel and is accepted to be the authority on what really happened. Lovers of the musical may have problems with this novel, since Andrew Lloyd Weber made changes in some characters. Madame Giry, for example, is much different in the novel; Carlotta plays a much smaller role; and Ubaldo Piangi doesn't even exist. In addition, Weber completely left out the important character of the Persian.
However, the Phantom's mystery is still here full force, and entire chapters are devoted to describing how Erik fools the incredulous management. The characters are not very vivid, though; Leroux was journalist, not a novelist, so the characterizations are sparce and vague. In certain places, Erik looks almost like a complete maniac (which I personally dislike and don't believe to be the case); Christine Daae, a snivelling shallow twit; and Raoul de Changy, a simpleton without a snippet of common sense.
All in all, however, this novel is fascinating because it is as close to a documentary of the affair as we will ever get. Leroux begins the novel by stating that everything he is about to present is factual. All Phans wishing to delve deeper into the story should begin here and use this novel as their stepping-stone to others.