It is a tough decision. It is almost 400$ to take the test. If you mess up a few questions, you may end up retaking it. That's another 400$. That's why many DAT resources,Feralis, Kaplan, Destroyer, CrackDAT update their materials. New versions have new questions with new explanations that you may see on your test. Old versions do not have it. Not knowing those questions may lower your score. I would chose the newest edition of any book, just to make sure I am not missing anything.