This out of print classic from Rizzoli entitled Jocks And Nerds is one of the best books I've seen on Men's fashion. Richard Martin and Harold Koda put it together in 1989. Nearly twenty years later the book serves as a great launchpad for inspiration and discussion.
They break down men's style into twelve categories: Jock, Nerd, Worker, Rebel, Cowboy, Military Man, Hunter, Sportsman, Joe College, Businessman, Man about Town, and Dandy. A great visual mix of photos, explanation and theory. I think more than ever great style is about taking a piece of all these types and making it your own, so you can't really fit into a category or genre.