There's always that one book, that book that just doesn't know what it's going to do to you, that book that is merely a gateway drug to the rest of the author's output. It might not even be representative of the author's career. Eye in the Sky: A Novel was the first PKD book that I read, and it prepared me in no way for his 1970s drug trip novels or his taoist masterpieces.
THis was my first Tanith Lee book, a werewolf story with Little Red Riding Hood overtones. And it shook me to the core. Remember Abyss books - a short lived experiment in horror from one of those big companies. The imprint gave us Poppy Z. Brite and something with skinned monkeys, but they also lured Tanith Lee away from her Daw house. I don't know if she could have written this with Daw. She is a fantasy writer after all. This is decidedly Dark Fantasy (and while many insist that there's no difference between Dark Fantasy and Horror, ask yourself when you last reevaluated all your childhood stories from a Stephen King novel)
The main character is a werewolf seeking his paramour. That's a simple story. But the way she tells it keeps you enthralled for page after page. Even the dead ship slaughtered scenes lifted straight out of Dracula feel compelling and shocking.
If you can find this book, grab it. Don't bother if it's through ebay, Amazon or your really creepy cousin. It's definitely worth the bother.