Here's one case where the movie was 100 times better than the book. It's no wonder that Leroux sold very few of these books during his lifetime because, quite frankly, the book was awful. The story idea itself, though, is interesting. Therefore, it's no wonder that it made it to the movies. In the novel, a disfigured man lives underneath an opera house in France and becomes obsessed with one of the opera singers. He seems to haunt the opera and makes demands that must be met lest the opera feels his rage.
The author really isn't very good at telling a story. There were a few very interesting parts that lasted no more than 2 or 3 pages, but they were few and far between. Most of the characters were very one-dimensional and indistinguishable except for the main three. The author has difficulty switching between scenes; one moment two guys are locked in an room filling with rising water, then they are sitting in front of a fireplace, and then they are above ground. The author also doesn't explain his settings very well; is he talking about a proper house or rooms underground and how in the world does a forest of trees suddenly appear in an an underground room? Some of the problems might have been with the translation (such as the mistranslation of "shadow" as "shade", but I think the main problem was with the author himself.
I completely slogged through this book and really don't recommend it for a pleasurable read.