Jason - October 1964 by David Halberstam: As a Cardinals fan, I feel I should grab a book that is Cardinals-centric. I don't think I'm that interested in worshiping at the altar of LaRussa, so that rules out Three Nights in August (he's fine as a manager though) and instead I'll go with October 1964 by David Halberstam. Halberstam knows a good narrative and his book from the year notorious for the Phillies collapse is a great look at some of the best Cardinals and Yankees players of all time in the lights of the World Series.
Mark - Sandy Koufax: A Lefthander's Legacy by Jane Leavy: The book alternates chapters between a biography and an inning by inning recap of Koufax's perfect game on September 9, 1965. Leavy does a nice job letting us see what she learned about the pitcher and drawing us into the description of the game. He's a tough one to understand, seemingly aloof, but always a gentleman.
She taps teammates, opponents, reporters, players that were still in elementary school when he retired, and more for stories and insights. Her writing style is relaxed, but with a purpose. The one thing that did jump out at me is the use of some words that didn't quite seem to fit in a baseball biography. An example is the word denouement. It is used four times in the book. A bit of a speedbump while driving the reading car. But that is a minor quibble on my part.
Go to the library and check it out. Better yet, go buy a copy. You'll want to share this with your baseball buddies and probably will want to reread it in a few years.
Jon - The Hidden Game of Baseball by Pete Palmer and John Thorn: Where would our understanding of baseball be without Palmer, Thorn and this book? I read it in high school and it played a big part in my joining SABR. If for some reason you enjoy baseball statistics and have not read this book, you really owe it to yourself to find a copy and read it.