it is certainly possible to memorize the words in the Barron's book..I for once did it, but that was for the SATs. I was talking to this guy who wrote a book on grad school application and according to him, for science and engineering majors, departments don't pay much attention to your GRE verbal. It is good to have a high math score (around 750+) but schools look into your other factors such as GPA, recommendations and personal statement. Also, if you have done research, that helps. He actually said there are a lot of schools where GRE doesn't factor into your admission criteria. MIT, for example doesn't even request it because they know that your GRE score isn't saying bull about your ability to get through grad school. But if you are for example English or History major, then you need to have really good GRE verbal (I would say 700+).  And another thing I learned is that rather than spending time memorize the words, it good to develop a good reading habit. Practice the critical reading part so that you will have to spend way less time to boost your score.