I like Terry Pratchett very much; I think I have everything he has published. I like some of Mr. Butler's literary criticism of Pratchett. In particular, "Guilty of Literature, " edited by Butler, is excellent. But it's hard to see what help "Unofficial Companion" offers that the revised "Discworld Companion" doesn't.
Oh sure, there are a few things. Butler looks at the non-Discworld books, including both the "Johnny" series and the "Truckers" series, but I've always regarded those as Pratchett's lesser efforts. Butler and his fellow essayists also cover all of the miscellaneous publications, even such items as the Maps (Discworld, Ankh-Morpork, Lancre, Death's Domain) and, heaven help us, "Nanny Ogg's Cookbook." Even the "Science of the Discworld" books are covered. I guess I'd question whether they should have been included.
On the other hand, while some of the major characters are described, the descriptions aren't terribly insightful. Groups of characters - the wizards, the witches and the watch, for example - have their topics but the analysis of these groups is simplistic and sometimes just wrong. None but major characters are given their own topics, and largely repeat what's found in "Discworld Companion." Perhaps most importantly, the touches of light humor that grace the "Discworld Companion" are completely missing. It's all dreadfully serious.
And whoever proofread the "Unofficial Companion" is dyslexic. There are egregious errors on many pages, some of them the kind of errors that bring your reading to a complete halt. These are the kind of mistakes you'd expect in a knock-off paperback; not in a hardbound volume that goes for $50.00.
So what you're left with is a poorly edited, not particularly insightful, nearly humorless series of notes on Pratchett's works and major characters and locations. Admittedly, it covers all of the works, even the lesser efforts, but how much do you need to know about a map of Ankh-Morpork? "Discworld Companion" is much more fun and more complete in discussing characters and places. And if you can find a copy you can afford, "Guilty of Literature" offers much more insight and thoughtful criticism.
Three stars for a yeoman-like effort. But wait for the paperback.