Last year I took the ACT as a sophomore and received a 32 with no preparation. Now, after reading some of the science strategies from Princeton Review, and after studying for SAT CR, I am within the 33-34 range. What books should I buy to raise my ACT score to a 36? I have about 7 months to do it. I am most worried about the science and reading sections.
If you don't have them already, you should get the Real ACT Prep Guide and the ACT Black Book. The Real ACT Prep Guide, also known as the "Red Book", is a great resource for official practice tests. The Black Book doesn't have practice questions, but it's a companion to the Red Book in that it offers helpful strategies and answer explanations to go along with the official questions.
Another nice supplementary book for high scorers is Barron's ACT 36. It has many, many practice questions and examples and is extremely thorough in its coverage of the material. If you want to focus on the Reading section specifically, I'd also recommend Erica Meltzer's Complete Guide to ACT Reading for high-quality passage examples and strategies.