It is a very concise preparation book for the Natural Sciences CLEP exam which only hinges on a few topics for each subject area (physics, chemistry etc.) It is certain that the examinee will need other resources (college textbooks or study guides) for an optimum and effective preparation. That said, the review does not offer sample of tests akin to the difficulty of the actual one. The questions in the review are in majority conceptual, which is not the case for the real exam. Eventually, there is NO progression throughout the book; which makes it difficult for the examinee to evaluate whether s/he is ready to take the test. Overall because of the lack of concistency and reflection to the real exam, I will highly recomment not to buy this book on its own as a preparation guide.