This book is so good that if I were the sort to drunk-dial women from my past, I'd get good and drunk, call one up in particular, tell her to read this book, and then hang up. I was certainly sore tempted about a third of the way in. Fortunately for all concerned, I rarely drink anymore, and even when I did occasionally drink too much I still tried to maintain my dignity.
Posnanski is a hell of a writer. His blog is the most consistently interesting baseball blog out there. It was over there that I saw a commenter mention his regret that he never got to meet Buck O'Neil, and someone replied that if you read this book, you did. And that's pretty much on the mark. It's not really a biography, although many of the stories Buck tells are about growing up in the segregated South, life in the Negro leagues, and how he met his wife. But mostly it's just Joe and Buck talking while at a game, or Joe watching Buck interact with others in both good times and bad, as he accompanies O'Neil to various functions and ballparks.
One of the best stories from the book is excerpted in Posnanski's blog. I was going to repost it, but it's a bit too long, so just go there and read it. You'll be glad you did. And then get the book!