anything u put ur time into is worth something. cliffs ap has one major flaw although it has intensive information. cliffs i belive puts everything by facts and doesnt really explain anything and u kind of get bored. if ur good at biology then u should read it but if ur just a starter, u should get princeton review ap or 5 steps to a 5. i perfer 5 steps to a 5 if u remember some stuff from highschool about bio.