DD10 just finished A Series of Unfortunate Events. She's currently reading the Fire Thief trilogy, thanks to a recommendation from the ultimate books thread.

Would your DS like the Ranger's Apprentice series? That's one of my next group of books for DD. I don't know that they're particularly challenging, but I thought my DD would enjoy the story.

DD prefers books written for the middle school interest level, which makes it hard to find books at her reading level.