If you learn best from books then Kaplan has good books. I personally don't and couldn't study that way. For Organic, purchase Chad's videos. He's a DAT and MCAT tutor who made comprehensive videos for Organic and Gen Chem. He is the only resource I used to study for those sections and I had 20+ scores. I remembered nothing about the courses going in. Chad tells you exactly what will be asked on the DAT and how it will be asked. He also gives cheat ways of finding answers fast. For Biology, I only studied Cliff's AP Biology book 3rd edition. The biology section has changed a little for 2015, so there might be better resources for that now. Finally, purchase access to DAT Bootcamp. The first practice tests in each section are free if you make an account, so you can try it before you buy it. Bootcamp is a great way to study for the perceptual section and to test your knowledge levels on each section of the test. People who use Bootcamp consistently get 20+, so I highly recommend it.
Best of luck!