Kaplan books are great for content review... they had all the material I needed to know the first time I took the exam, what I particularly like about their book is that they have notes on the sides when a particular topic is relevant clinically, or of it's relation to another topic (like physical sciences) and especially, they emphasize MCAT favorites, and are great about tying different topics together (concentration gradients and nephrology is a great example)...
but the most important part for Bio is to take practice tests, because about 65% of getting the questions right is being able to take out the correct info from the passages, and to read the graphs... AAMC CBTs are A LOT more indicative of the Actual MCAT Bio section than Kaplan, that's all I can say