My recent favorite: The Planet Remade: How Geoengineering Could Change the World by Oliver Morton. Engagingly written -- I could hardly put it down! -- comprehensive, thorough, and optimistic without being credulous, this book contains a wealth of information about the "earthsystem" (as Morton likes to call it) and the effects we're already having on it as well as those we could potentially create intentionally. The book makes an excellent case for expanding research into geoengineering, and I hope it gets widely read.