Sort of a summation of some of David Mitchell's articles as featured in the Observer newspaper, he annotates them and (quite possibly) edits them. I'm unsure as to the specifics, but that's not particularly a bad thing.
As one would expect, the mini-essays in this book are on a variety of topics, though most of them could be described as "British". It is an enjoyable book for its humour and scope; no fan of Mitchell could deny that it is definitely him speaking. I enjoyed his opinions and style of writing and found most things to be very interesting, even, dare I say it, thought-provoking.
I would suggest it is more of a dip-in-and-out book rather than something you read all the way through in one (or a few) sittings, much like a newspaper is issued periodically as opposed to at the beginning of the year. It is funny, at times quaint and very much David Mitchell.