Alan has illustrated dozens of fantasy books, including some nonfiction, and many more covers. Several works by J.R.R. Tolkien are among his most notable interiors: the Tolkien centenary edition of The Lord of the Rings (1992), a 1999 edition of The Hobbit that has been boxed with it, and Narn i Chîn Húrin: The Children of Húrin (2007).