If you've already taken some AP courses in the past, you probably know about the enormous catalog of AP review books that are available for purchasing and, hopefully, that most of them are useless. I remember in high school I would often go to the library and rent out a sizable selection of AP review books, go home, and leave them collecting dust for two weeks. I would do this often and either never read them, or realize that they did not help the slightest bit. Here are some pointers:
-Take this advice with a grain of salt. Not all review books are useless. Some have good practice questions and summaries for the information that you have learned in class. Ask your teachers if they recommend any to purchase from your local book store (they will probably make an announcement at the beginning of the year or nearing the AP testing weeks). Never use the review guide as a substitute for your teacher, but use it as a crutch if necessary.
-Don't purchase the books if you can help it. Your school or city library most definitely has the same books as, say, Borders. You won't have the liberty to write in the books, but that's what notebook paper is for, right? If you obtain them near AP test time (if you can find any copies), you will probably be forced to return the books by the due date if someone has a hold on them. If you're lucky, you could renew the book and keep it for yourself. In any case, try to save money! You're paying a lot for AP tests, even if you're taking one.
-Review books try to refresh your memory. If you've done well in your AP course, you're not going to learn anything new from the book. The Princeton Review, for example would refresh everything that you learned earlier in the year, give you some tips, and then provide several practice questions to prepare you for the exam. In my experience, the questions from review books are nowhere near as helpful as what you get from your teachers, primarily because your teachers use questions straight from previous exams. It is also very easy to be misled by the review questions in these types of books because they are simplified to make yourself feel like you know more by reading the guide.
-Your textbook and lecture notes are fantastic guides. Not only do you have an incredible supply of practice problems, but all the information you need to know is in a pile of notes. Of course, review books weed out some unimportant statistical information and minute details; furthermore, once they've done that, they effectively summarize the information. What your textbook tells you in 30-40 pages will be reduced to a handsome <10 pages. In essence, the review books are time savers so that you don't have to burden yourself with the 5-pound textbook you have in your closet. Again, if you have done well in the course, the review guides may be effective at forcing you to recall the information, thus keeping it fresh in your mind.