Tithe by Holly Black. I discovered this when a local bookseller created a new section for teens in the store. While browsing in the nearby stationery stacks, I looked up and this cover caught my eye. It was the first teen book I've bought. (I don't remember there being any teen books when I was teenager. There was certainly no section for it in my local bookstore.) Anyway, I loved this story about modern faeries. The fae in Tithe are just like the teens in the story (and in real life), at times ferocious, at others endearing. They share no resemblance to any fairies that Disney would approve of and are better for it. I loved this book for living up to its considerable promise.
Guilty Pleasures by Laurell K. Hamilton. One of my favorite series. The first books were so original in their style, combining horror with crime fiction. Preternatural forensics? Yes, actually. With Anita Blake as a vampire assassin/necromancer. This is the original that so many other authors have gone on to copy.
Storm Front by Jim Butcher. "Harry Dresden,Wizard." The words are printed on the door of Harry's place, much to the bafflement of local delivery men. When there are occult crimes in the offing, Harry can be hired to investigate them, and, in Harry, Mr. Butcher's created an enormously likable protagonist. Harry's often an underdog despite considerable skills, and it's fun to watch him battle the universe's evil forces. This series was the basis for a terrific TV series on the Sci Fi channel called The Dresden Files.
I've mentioned Jasper Fforde in other posts, so I would be remiss if I did not include his remarkable and remarkably odd books in this recommendation list. He reports that when his agent was trying to sell the first book, she had difficulty describing the premise and so asked editors to "just read it." I really like that approach. All I'll say is that the main character's name is Thursday Next and people are able to get into books and to kidnap characters right from their pages. If you want to read something wonderfully original, witty, and off-the-wall, I give you The Eyre Affair.