Hi!
I’m planning on taking the AP Psychology test in May, and possibly the AP Statistics one too AND on taking the SAT Subject Test for Biology and Math II this June.
What books do you recommend using for studying for those?
Thanks!
For AP Psychology I recommend 5 steps to a 5, I also found the princeton review at my local library and used both to fill in the gaps. I’ve found that although review books all cover the same material some books go into more detail about one thing that the other book leaves out. If you are able to go to your local (or highschool) library and check out multiple review books I would recommend doing that.
I never took AP stats or SAT 2 exams so I don’t want to give an recommendations for those.
I’ve personally had a mediocre experience with the Barrons books (not sure if I spelled that right) but I am self studying Psych right now out of a Princeton Review book as an outline and the internet as my guide. I go through each chapter and brush up on the topics, then I read online about them from various, mostly scholarly sources, and then I do some practice questions. I am doing fine as it is.
As for SAT II, I can’t speak for either of the Biology tests (never took either of them) but Math II is easy enough to wing if you’re good at math and have had a thorough math education up to this point. My school system’s math program has some holes in comparison to the SAT II Math II test so I also used the Princeton Review book for that and that worked like a charm.
Best of luck with your exams! And, good for you for taking your SAT IIs before you start applying, I can’t say the same for myself 
AP Psychology: Barron’s. I used basically nothing but this book and got a 5. (My AP class was a joke.)
SAT Bio: Princeton Review. Used nothing but this book and got an 800.
SAT Math II: Barron’s and John Chung. If after going through Barron’s you’re already confident (i.e., consistently getting 800’s on the Barron’s practice tests), you can skip John Chung.
Thanks for all the responses, everyone! I really appreciate it. 
@glower101 bit late to this thread. For AP Psychology, if you were really lagging on one particular area, use the OpenStax Psychology book at https://openstax.org/subjects. It’s really good.
For a prep book, I’d recommend Barron’s, I really liked it.
not the question you asked, but if you are self-studying to impress colleges with the # of APs you have taken, it’s not going to help as much as using that study time to get better in-class grades or using that time to deepen your ECs. If you are doing it b/c you are applying to international unis that’s a different story!
Use Barrons for Psychology. This AP exam is simple memorization and logic, it will be manageable. For statistics, either PR or Barrons will do as well. This exam is also on the easier end of the spectrum.
As for the subject tests, Math II will take a lot of practice, unless you have a strong Math background. Biology, likewise, will take a decent amount of time to familiarize yourself with the material. I would recommend Barrons for both. For both tests, I simply read through the Barrons study book, took the included practice tests, and ended up doing well.