I know what you're thinking. "Why did he post this? It's a classic! There's no need in pointing out the obvious..." Well, yeah, Robert Louis Stevenson's Dr. Jekyll and Mr. Hyde is indeed a classic and everyone capable of reading a novel should have already read it by now.
The problem is, very few people have really read it, choosing to watch one of the billion movie versions instead, which is a pity given that: a) the book is much more interesting than any of those movies; b) in comparison to other classics of the genre, such as Dracula or Frankenstein, it has aged remarkably well; and c) it is by far the best werewolf novel in existence!
Now I know this last statement does not ring true but it is completely and utterly faithful to the truth. The rational Dr. Jekyll may never turn into a proper wolf-like creature - he doesn't even grow hair - but his transformation into the wild Mr. Hyde is 100% werewolf-like. Think about it, and let it sink. The novel also boasts curious dualistic imagery with each side of the main character represented by appropriate surroundings; Dr. Jekyll by polished house and well-respected friends, and Mr. Hyde by dirty streets and shady by-standers. This sense of dualism placed in the hearts of all men is most certainly the basis for the werewolf myth, and all good werewolf stories essentially go back to it.
So, why don't we cut the chase? If you'd like to read the novel, you can get it HERE... or you can simply go out and buy it in the nearest bookshop for less than 2 bucks :)
Update: On May 8th Universal announced a "modern retelling" of Strange Case of Dr. Jekyll and Mr. Hyde with Keanu Reeves attached to star in it. Was my post foreshadowing future events? :)