Watch out for the purple book, it covers tons of stuff and it gets you into the habit of being careful and working through each problem. This is not at all like the GRE. I spent last summer using the book and I progressively took each of the 4 available practice exams. I found that as I went through the purple book, I understood more, yet the last practice test I took I actually did worse!
In retrospect, I realize that I understood more physics, but I was taking longer on the actual test. If you know a little bit about every question, you'll attempt to actually complete each question thoroughly, however, it simply takes too long. If you do use the purple book, before the test go over the actual exams. The actual GRE exam tests speed as much as it tests understanding. Look for limiting cases etc. The purple book will have you doing unreasonable calculations and you'll get used to it. The problem is that doesn't represent the GRE. You may understand more physics, but it could hurt you if you're not careful. Whatever you do, definately hunt around online to get the practice tests.