"Pushing the Limits" by John Howard and Peter Nye. The story of John Howards career, focusing on the period from 1968 to 1978, when he was America's leading road cyclist. It is a good overview of American cycling in the "bike boom" when more Americans bought road bikes than in any decade in history.
"Delong's Guide to Bicycles and Bicycling" by Fred DeLong. The best book I've seen on bike design, bike fitting, and owner maintainance of a bike.
"Richard's Bicycle Book" by Richard Ballantine. Many editions between around 1970 and 1995. It is fun to compare editions, as Richard's attitude changes over the decades. In 1970, road bikes were the ONLY bike to buy...then he fell in love with 'bent's, then he became passionate about mountain bikes.
"23 Days in July" by John Wilcockson. One of the best "inside the Tour de France" books I've read.
"The Art of Urban Cycling" by Robert Hurst. Although 246 pages is a LOT of reading (the world needs a good 20 page guide to the art of urban cycling) Hurst does a great job of discussing the issues involved in riding in the mean streets of urban America. If everyone who rides in heavy urban traffic reads and re-reads this book, it will prevent a lot of needless stress, injuries, and even fatalities.