For O-Chem and Gen Chem, all you need is the Kaplan book. Period. Go with knowing every reaction in the Kaplan book and you will be just fine, unless you are gunning for a 23+, then mess with the other books. I used Destroyer for Biology, but it was way more detailed than necessary for Gen Chem and O-Chem. It didn't spend enough time on the basics that were actually on the DAT, and spent too much time on crazy exceptions that just ended up confusing me. However, for Biology, Destroyer is the way to go.