I always suggest the book I'm linking to below because it goes over multiple different classroom management systems and helps teachers understand common elements across different programs, and some of the research that goes into the development of those programs. Very few strategies in any one system/program are unique or novel to that program - most are cleverly described/packaged best practices that have been researched in other contexts, then put together for ease of use.
The book below describes a lot of these programs, so you can see which one(s) you like, and chose to buy those specific books. If you just arbitrarily chose a book, you may find that you like it less, or may miss something even better. You will also be able to pull in strategies from different programs and fill gaps that certain programs have.
Love and Logic and How to Listen so Kids will Talk and How to Talk so Kids will Listen (dang that's a long title). I saw a dramatic improvement in my relationship with students after trying to implement those suggestions.
I'm a first year and have been reading/training with Fred Jones--I highly recommend it. Some of his concepts seem like simple common sense tactics, but he makes you aware of everything you say, do, act and he teaches you to be consistent! Good luck
I love "Setting Limits..." too.
Also, while not specifically classroom management, this one is great: "Backtalk, 4 Steps to Ending Rude Behavior in Your Kids." It's based on logical consequences for behavior. Here's a quote from the back of the book: "You'll learn how to recognize backtalk, how to choose and enact a response that will make sense to you and the backtalker, and when to disengage from the struggle and move on." I re-read it periodically, and always get something good out of it.