This is the current listing of Discworld books, as of July 11, 2000. I will try to keep this list current, as new books come out.

Novels by Terry Pratchett
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
Feet of Clay
Hogfather
Jingo
The Last Continent
Carpe Jugulum
The Fifth Elephant
The Truth
Thief of Time
The Last Hero
The Amazing Maurice and His Educated Rodents
Night Watch - Thanks Heisenberg & Great Neb
Monstrous Regiment
Going Postal

Discworld books by other authors
The Discworld Companion by Terry Pratchett and Stephen Briggs
The Science of the Discworld by Ian Stewart
The Science of the Discworld 2 by Ian Stewart thanks Zerotime
The Streets of Ankh-Morpork by Terry Pratchett and Stephen Briggs
The Discworld Mapp by Terry Pratchett and Stephen Briggs
A Tourist Guide to Lancre by Terry Pratchett and Stephen Briggs
Death's Domain by Terry Pratchett and Stephen Briggs

The same as most everyone else who have written on the Pratchett nodes, I think that the Discworld books are incredibly funny and yet also thoughtful. I encourage everyone to give them a try. I don’t think you’ll be disappointed.