My brother got me this for Christmas. I'm most of the way through it and really enjoying it.
It seems to be compiled from his blog posts and deals with different types of strong ale. He goes into a lot of depth using brewing records, articles, brewing texts and all sorts of historic stuff that gives a really good idea of how brewing was done in the past.
It's a thick book with quite small text so you get plenty of bang for your buck.
There are some common styles like Barley Wine, Scotch ale and Imperial Stout, but also some I've never heard of, like Arctic Ale.
If you know him you'll know what you're getting. Plenty of dry humour and facts and figures and also lots of common myths proven wrong. It's really interesting to compare his records with what other books say. The main thing I took away is that the styles were pretty loose and have changed a lot so it's very difficult to define them all.
If I was going to be mean about this I found there were a few sections that were repeated in the Scotch ale bit and the odd typo but those are very minor gripes. It's a great book and I'd recommend it to any brewer.