Even though you're probably familiar with standardized tests from your experience with the SAT or ACT, it's a good idea to find a preparation book that will familiarize you with the test and give you strategies for answering the questions and managing your time.
GRE: Practicing to Take the General Test, 10th Edition
Published by Educational Testing Service, which also prepares the actual GRE each year, this is one of the best GRE prep books because it comes from the people who know the test best. This prep book contains questions from past tests (both verbal and mathematical components).
Cracking the GRE with DVD, 2011 Edition
This guide breaks the GRE down into easier-to-understand components so that you can get a handle on how to approach the test as a whole.
Also check out Barron's GRE, 18th Edition for a similar book to Cracking the GRE with DVD.
For many people, the best way to improve a score on a standardized test like the GRE boils down to rote repetition of question types. Whether you opt for a set of complete tests to practice from start to finish, or a series of questions to help drill the formats and content into your head, make sure you incorporate past test questions whenever possible.
1,014 GRE Practice Questions
Published by the Princeton Review, this study book contains exactly what it states in its title: over 1,000 actual practice questions to familiarize you with the test's format and some of its content, too.
Nova's GRE Math Prep Course
If you haven't glanced at a math problem since Intro to Calculus as a college freshman, you may need to pay extra attention to your quantitative skills with Nova's GRE Math Prep Course.
Conquering Vocab: The Most Effective Way to Learn GRE Vocabulary in the Shortest Amount of Time
This book contains reading passages that will teach you new vocabulary words without memorization or long study sessions by contextualizing them in absurd short stories, so you won't soon forget what "abstemious" means.
As of Aug. 1, 2011, the GRE test format will change, so it's important to make sure that whatever edition of study/preparation book you're using is the most up-to-date possible. If you're taking the test before Aug. 1, 2011, any of the above listed test preparation books will help you. If you will be taking the test after the date of change, these books will still be somewhat relevant, but keep checking the Educational Testing Service site for more information about how to prepare for the new format.
One of the unique characteristics of the GRE is its format. Unlike the SAT or LSAT, for example, the GRE is completed via computer. Since the majority of test preparation materials are available in hard copy, it's important to understand that the actual test taking experience will be markedly different from the experiences you've had in the past, and that this may require additional adjustment on the test taker's part.