Book Discuss

Anyone have any brilliant notions on an appropriate (possibly YA) fantasy-type book to give a boy turning 17? His reading skills are quite advanced. As I understand it, his reading abilities are easily equivalent to most adults, although the book's contents should not be too graphically sexual.

He has enjoyed the Harry Potter books, as well as Lord of the Rings. He loves David Gemmel's novels, but has read them all. Likewise with Raymond E. Feist books (including the Empire series written by Feist and Janny Wurts.)

EDIT: I bought the two books today - Good Omens by Terry Pratchett and Neil Gaiman, and Sabriel by Garth Nix.
Thanks to all who gave their suggestions.