I know that lots of sites are doing April Fools gags today, but I would rather talk about Terry Pratchett’s wonderful creation Discworld which overall is funnier than most of the pranks going on. In all it comes to about 40 books these days, with hopefully at least a few more waiting to make it into our hands. From the first story The Color Of Magic to the most recent release Raising Steam, they are every one of them poking fun at all aspects of small mindedness, bureaucracy, prejudice, and superstition. There are a large number of wonderful recurring characters that you will find yourself relating to, often because they make up the limited number of sane people (and sane not-people) to be found in a given tale. They tend to come in groups, like the City Watch, the Witches, Ahnk-Morpork, the Wizards, and Death (yes, Death is both an individual and a group; see Soul Music, or perhaps The Death Of Rats).
The Discworld universe is in a steampunk/fantasy branch of the Multiverse, where wizards and engineers have an equal hand in creating the future, and humans share the land with a full range of other races, including Golems, Vampires, Dwarves, and Igors (the last very handy if you are suddenly in need of transplanted organs and limbs). Figuring out which order you should read the books in can be difficult, I recommend using the group approach. Go to the Novels chart on Wikipedia to find the earliest story instance of each group. Read each one of them, and I feel confident one of them will become an instant favorite, even if you don’t particularly care for the others. Then read through all of the novels in that group; by the time you finish that set, you will have met enough of the characters and picked up enough of the background for the other groups that you will know which one you want to read next. You can also read them in story-line chronological order for each group, either method will do nicely.
Sooner or later you will have read everything he has written about Discworld, but do not despair! He has written other stuff, including an excellent collaboration with Neil Gaiman. And there are four Discworld TV miniseries released on DVD, 15 stage plays have been published, two feature length animations have been created, a number of fan productions from around the world have been released into the wild, and a ton of radio plays of the stories have been recorded by the BBC and others for you to enjoy as well. There are several projects in production, including a 13 episode TV series about The Watch, a miniseries of Unseen Academicals, and the fan production of Troll Bridge. Once upon a time Sam Raimi was going to do a feature film from The Wee Free Men for Sony, but that fell through. All is not lost though, because Rhianna Pratchett announced she was going to pick up the project instead.