The Phantom is a heck of a lot creepier than in the movie. Just sayin'.
If you want to read more classics, but don't have time for really thick or dense books, I'd recommend this one. It's short and has enough thrill to keep you going, even with ornate details and the overwrought setup. (I mean that in the best way. It really works for the tone he's going for.) It also has an element I can't describe as anything other than Frenchness.
Things I liked: fast pace, overtones of horror that fit really well with the theatrical scenery, the way side plots got worked in, the Paris opera house, Christine, the Persian. Though he doesn't spend a lot of time forming their characters, Leroux gives us a vivid sense of what they're like. I was more impressed with Christine than I thought I'd be.
Things I didn't like: Raoul. I've always thought he was a bit wimpy, and though Leroux takes pains to tell us that he's brave, we get no sense of what he's like other than obsessed with Christine to the point of selfishness. Kind of creepy.
But not as creepy as the Phantom.