If I had to recommend just one book about classroom management, it would be "Tools for Teaching" by Fred Jones. Fred Jones has observed teachers (good and bad) in classrooms for over 30 years and through observation and experiment has distilled the essence of good classroom management into this book. I highly recommend it. Failing that, Fred has put summaries of his classroom management strategies on his website at
http://www.fredjones.com/Tools-for-Teaching/Tools-for-Teaching-main.html
These articles are excellent.