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,
A Confusion Of Princes), he has several series out, including the
Old Kingdom series, the
Keys To The Kingdom heptalogy, and
The Seventh Tower hexalogy.