I have to admit that I "only" read the German version of this book ("Der ganze Wahnsinn", Piper Verlag) - and I'm pretty sure I won't be able to read the English original, regarding the fact that it costs about 200 GBP on Amazon.uk's "Marketplace" at the moment. (So, unless it's going to be re-released some day,...)
Anyway.
This book is basically a compilation of some of Terry Pratchett's short stories, some prologues and introductions he wrote for Discworld computer games and/or CDs, and some "essays" and (at least one) travel report(s). And as far as I know, all of them have already been published in SF magazines, Fantasy magazines and/or other magazines and fanzines he'd been asked to write for. I knew none of those stories etc., since I'm (obviously) living in the "wrong" country.
Again: anyway.
Story-wise, there are some real gems in there, but since I don't know the English titles, I can't tell you which one I loved best. If you come across it: I loved the short story with Santa, the computer and the teddy bear, the short story with the fictional character "Erdan", which came to "life" and, last but not least, the story about Wayne and his records and Death.
I loved the small "insights" Terry Pratchett allowed the reader to have on his work: his views on writing, what writing actually means to him, what's important to and what had influenced him. A very nice, interesting and entertaining read. I don't know whether it's any good to non-Terry-Pratchett-fans, though, but I like to think it is.