Frankly, this book does not help the critical reader. I tried and didn't get as good an understanding as any other test prep book I've ever read, in any subject. There are numerous errors including spelling, incorrect answers and concepts. Not only that, but the drawings were poor - I wondered what kind of program they were using to make such images. The end product looks like what you might get if you had 5 days to finish it. Only buy if you get a tremendous deal.