I used the Princeton Review GRE prep book. (I did not use any of the others, so I cannot make any comparisons.) I thought the book was worthwhile. They teach you how to play ETS' game.
- The tips given for the math section are very helpful. They'll help you dredge up some of those math skills that have atrophied since high school.
- They give you a cookie-cutter format for writing the essays (since the essays are graded from a rubric). I just followed the format to the t for my essays, and I, an average writer, scored well.
- The vocab words given in the Princeton book were on the test. I made a flashcard out of each word and went through the whole stack a few times. Then, I took out all the cards that I know the definition to, leaving just the cards you have problems with. You can learn 300 definitions pretty quickly this way.
-PD