Garth Nix

Australian author Garth Nix specializes in what's now called "Young Adult" fantasy--but don't let that throw you. He has the uncanny ability to take fantasy Cliche Storms and convert them into pure horror. Pray that his dark gift never reaches the people who write the "American Girls" books.

He also is a big fan of Capital Letters Are Magic, and has a kind of awesome name.

In addition to a few standalone novels (The Ragwitch, Shades Children), he has several series out, including the Old Kingdom series, the Keys to The Kingdom heptalogy, and The Seventh Tower hexalogy.