hi, i took the kaplan course and read the kaplan book and it seemed that bio was a bit too generalized in that book. so~ i bought cliffs ap bio, 3rd edition. i think this is the latest edition available, less than 20 bucks, and totally worth it. its explanations are clear and i like how the chapters are organized. there is also much more important detail we probably need to know. the book also includes a little quiz at the end of each chapter, and two full length practice exams at the end. i think it's a must!