He's got a new non-fiction collection out, called A SLIP OF THE KEYBOARD, with a foreword by Neil Gaiman. The range over a wide array of topics -- everything from an hilarious account of an Australian book-signing tour to the more serious right to die with dignity.
Pratchett can make you laugh, even while he's cutting your heart out with a scalpel, or making you re-think what you thought you believed in. Whether you've read any of his novels or not, this collection of non-fiction will make you both laugh and think.
It'll interest you in either trying his fiction, or revisiting it. There are several of his novels that I re-read at least once a year.