The Phantom of the Opera: The Original Novel 
by
Gaston Leroux
Before the Andrew Lloyd Webber's musical, there was Gaston Leroux's  original novel "The Phantom of the Opera". I have never seen the  production stage, and I knew only a few things of the story, so when I  reached the middle of the narrative I was surprised because it is  totally different from what I expected. And it was a great surprise. 
More than a love story, "The Phantom of the Opera" is a gothic tale  of obsession --leading to madness. The Paris Opera House and its hidden  rooms, and underground are perfect place to develop a horror story.  Leroux noticed this potential. His descriptions of the place are creepy  and in the end we start wondering if it is not a true story indeed.  
Leroux was very smart, writing a novel like he was only reporting  something --and not creating a work of fiction. Therefore there are  police reports, newspapers' scraps, witness interviews. More than a  narrator, the person who is telling the story is only gathering useful  information for the reader. 
His characters are real human beings --even the `ghost', than  throughout the narrative we realize that he is the one with most human  characteristics. Sometimes, Christine is a little stereotypical, mostly  when she says she wants to be `the mistress of her faith' or something  like it. And so is Raoul --but that doesn't diminish the qualities of  this engaging novel. 
All in all, this is a French classic that I highly recommend  --however one must be patient because the narrative is a little  confusing and slow sometimes, but never boring.