This article is from the Pratchett Newsgroups FAQ, by Orin Thomas firstname.lastname@example.org with numerous contributions by others.
Here is a list of Terry's Discworld Book Titles. A more complete listing
including the Nome, Pre-Discworld, Collaborations and Young Adult books
(including ISBN etc) is in the PRATCHETT BIBLIOGRAPHY.
The Colour of Magic, The Light Fantastic, Equal Rites, Mort
Sourcery, Wyrd Sisters, Pyramids, Guards! Guards!, Eric
Moving Pictures, Reaper Man, Witches Abroad, Small Gods
Lords and Ladies, Men At Arms, Soul Music, Interesting Times,
Maskerade, The Streets of Ankh Morpork (with Stephen Briggs),
The Discworld Companion (with Stephen Briggs), Mappe of the
Discworld (with Stephen Briggs),Maskerade, Feet of Clay,
The Pratchett Portfolio (with Paul Kidby), Hogfather, Jingo,
The Last Continent, A Tourist Guide to Lancre (with
Stephen Briggs), Carpe Jugulum, The Science of the Discworld
Death's Domain, The Fifth Elephant, The Truth, Thief of Time,
The Last Hero, The Amazing Maurice and his Educated Rodents and
Science of Discworld II.