I've just finished reading this book in the sum total of an hour, but i still can't decide whether or not it's actually any good.
It certainly starts well- the first few chapters are intriguing and pacey. However, as the book progresses, it assumes a structure of distorted, disconnected passages depicting various dreams or dream-like experiences. Granted, the subject matter surely lends itself to a style, but it diminishes any form of plot to the point where the book becomes a series of meaningless waffel which is dreary and boring. This is a far cry its excellent commence.
That said, Garland certainly shows a flair for expression and through the central character, although left relatively unexplored, he portrays some very empathetic and interesting emotions.
Overall, the central theme of the book is a very original and dark one, but the author could've done so much more with it. Although good in places, the book is ultimately flat and bland- the climax being as poor as the build up to it. If the exact same script was written by a first time writer, i doubt very much it would be published. It seems this is another example of "established" authors getting away with writing on reputation rather than merit.