I'm actually taking the class right now, but after doing a lot of looking around and talking to people who have taken the test before (and scored well), I chose the Princeton Review for several reasons:
-It has a large section on techniques for scoring well on the multiple choice and on the essays
-It is relatively concise/to the point
-It makes a lot of connections between cultures, traditions, etc. and shows how things have changed over time, all of which is important for the essay portion of the test
-The book is actually fun (or at least not boring) to read because the authors used some humor and an appealing writing style
-The multiple choice questions are very similar to what you will find on the actual AP; they ask you to make connections, not just recall a certain fact
Problems with other popular review books:
-Barron's is more like a textbook than a review; it has a ton of information you don't need. The multiple choice and essay questions are also not representative of what you will see on the AP
-5 Steps to a 5 is more about test taking strategies and has less of a review
If you feel up for getting two reviews, I would get Princeton and 5 Steps. But if you just want one to do the job, I would stick with Princeton.
Hope that helps!