I'm thinking of ordering these books. Are they helpful as review tools?
The Powerscore book for SAT Math is relatively helpful, but the one for Reading isn't so great. The Math book has a helpful guide that breaks down questions into different types and gives you a frequency rating for each type of question so that you know which topics to prioritize. It also has a fair amount of practice questions with detailed answer explanations. You can read more about this book on PrepScholar's list of the best books for SAT Math.
The Reading book, on the other hand, is too focused on vocabulary. The new version of the test won't have any sentence completion questions, so this is especially unhelpful. It also doesn't provide many strategies for approaching the specific types of questions that appear on the test. It will give you tips to improve your reading comprehension, but it doesn't fully address the challenges that are unique to the SAT. You can read a full review of the book here.
Source: SAT prep tutor