I would recommend starting off with the Kaplan blue book. This will give you a good foundation in all sections and give you some practice tests for the DAT. You should use this book before moving on to something like DAT destroyer, especially if you've had some time off from science classes. DAT destroyer is more of sets of practice questions with detailed answers that are probably more helpful after you have a foundation. I also recommend Topscore Pro - its a CD with several practice tests that simulate the actually exam fairly well. Also, kaplan is a little bit weak in the biology section so you may want to consider getting something like Schaum's outline of biology, or simply use your college text book to brush up on areas that kaplan doesn't cover well. As far as prices, Destroyer is about $150, Kaplan about $40, Topscore about $50, and Schaum's is about $15.
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