I wrote the GMAT recently. I had used a couple of books for a few days as study aids.
I was really disappointed in how they advised you to study. It was all teaching for the test type stuff. The math sections in particular advised you to not solve algebra problems, but to just plug in numbers, or to work backwards from each given answer. It works (mostly) because the test is multiple choice, so you can verify guesses quickly. I found that I could do the algebra faster than I could do arithmetic, so I didn't follow that advice. The thought of using a number to verify an algebra theorem really irked me as a mathematician. Proof by example is never acceptable.
I ended up writing a practice test before any study at all, just to get a feel for it (and for what the questions were asking). Then I studied section by section, iterating through the advice of each of the books per section. The three treatments of each test section reinforced each other. I did practice questions when I felt I needed to, but that wasn't very often. After finishing all the sections, I did another practice test to see how I was doing.
Kaplan's GMAT comprehensive program had the best strategy and primers for each section of the test. Kaplan's GMAT 800 was a little more condensed and offered a good summary of the other book. The Official guide for GMAT review offered me my last pieces of advice before moving on to the next section of the test.
There may be better books out there, but these three did fine for me. Although none of them were particularly helpful for the "sentence correction" part of the test.