My counsel is if you find them, by old one!
I have prepared the GMAT, and I study on all kind of books, this is my ranking:
1) Manhattan, the best, expensive but really good (they normally require for exercise the official guide, so you need buy them together. (Read the free guide that they give on their site.
2) The official guide, realistic.
3) The Princeton Review, good explanation.
4) McGraw, Hill a bit too easy, but I love the 6 GMAT test.
5) Kaplan, good for the difficulty of exercise but not a good explanation. .
My counsel does not give extra time at the beginning and try only to be more precise at the beginning.
Finally, I find more exercise on Coordinate Geometry than any books have prepared me. But still nothing more than triangle.
And as you can guess I am not English.