Cloud Atlas was one of the best books I read last year. Not having been familiar with David Mitchell beforehand, I was surprised and impressed by the Russian-doll storylines and the diversity of writing styles and characters it encompassed. I'd heard virtually nothing about Black Swan Green before purchasing it, and that might have been a good thing, since it's nothing at all like Cloud Atlas.
The blurbs on the back cover compare it to Catcher in the Rye, but I think Lord of the Flies would be a more apt comparison, minus Flies' bleak ending. Coming-of-age stories and kids-are-cruel stories are a dime a dozen, but rarely does one create such a believable world as Black Swan Green. There's almost nothing in the book that rings false. It's not over the top, and it's not particularly symbolic. It's a lighthearted but sobering reminder than being a kid isn't the easiest thing in the world. Its structure is fairly standard, although there is something of a minor revelation at the end that ties together the book, which plays something like a series of loosely connected vignettes.
The other pleasant surprise of Black Swan Green, besides its overall quality, was the expansion of the story of Robert Frobisher, a character from the best story in Cloud Atlas. Such an inclusion could have been jarring, since the books are so different in tone and context, but it works wonderfully, dovetailing nicely with Cloud Atlas if you've read it, and playing as just another sideplot if you haven't.
This is a good book.