In addition to products designed for the , you can find a variety of general vocabulary-building books in the reference section of any decent bookstore. One type emphasizes and is organized by word roots and prefixes. Knowing roots and prefixes is the key to making educated guesses when it comes to unfamiliar words on the test. Put this type of book at the top of your vocabulary resource list. But bypass most other general vocabulary builders, at least for prep. Here are the most common types—and why they’re not worth the bother: