He has illustrated several fantasy books such as the centenary edition of The Lord of the Rings, The Children of Húrin, Faeries (with Brian Froud), Lavondyss by Robert Holdstock (as well as the cover of an early print of this book), The Mabinogion, Castles and Merlin Dreams. He won the Kate Greenaway Medal for illustration in 1993 for Black Ships Before Troy and the Best Artist Award at the World Fantasy Awards of 1998.
Lee and John Howe were the lead concept artists of Peter Jackson’s The Lord of the Rings movies. He illustrated many of the scenarios for the movies, including objects and weapons for the actors. In 2004, he won an Academy Award for Best Art Direction for his work on the third film in the trilogy, The Return of the King. Lee has also worked as a conceptual designer on the films Legend, Erik the Viking, King Kong and The Chronicles of Narnia: The Lion, the Witch and the Wardrobe and the television mini-series Merlin. Lee recently released a portfolio of his conceptual artwork for the Lord of the Rings film trilogy, entitled The Lord of the Rings Sketchbook.