Definitely Barrons for Math II and World History
If you want a 800 on US History, i would advise reading the AMSCO AP Exam Prep book (a long read.. but that's what it takes for an 800).. AFTER reading AMSCO, read the Kaplan SAT book.
If you simply want a good score (750+), just buy the Kaplan US Hist SAT II book. It's easy to read, clear, and concise.
