GRE Prep by Magoosh Paperback – December 7, 2016

The explanations in this book are vague and indirect. For example, they tell you that you can't cross-cancel proportions, but they never explain why. They show the proper way to cancel proportions, but they don't explain how they did it. You're left to figure it out on your own. Yes, that's a nice learning experience, but in some cases I don't have the background knowledge to understand why they did what they did. This is why your math teacher always says, "Show your work."