The best books to prepare for GMAT are:
The Official Guide for GMAT Quantitative Review
Though this book does have a several sample GMAT questions that go beyond the primary GMAT Official Guide, you may not want to go for both. Instead, you could get the basics sorted out with the Official Guide 2015 and then look for an advanced level guide for the quantitative section.
Kaplan GMAT Math Workbook
There have been lukewarm responses to this guide. Some have found it to be good to get the basics in place. Others who were expecting many more difficult 700-750+ questions have not been too impressed.
The Official Guide for GMAT Verbal Review
This verbal guide continues the good work done by the GMAT Official Guide. There are more real GMAT questions to give you practice on how the real test would feel like. Don’t jump into these before getting the verbal concepts clarified.
Manhattan GMAT Sentence Correction Strategy Guide
GMAT Sentence correction is a pain area for most non-native test takers. The Manhattan SC guide has been a favourite among Indian and international MBA applicants for several years.
Kaplan GMAT Verbal Workbook
This book just like Kaplan’s quantitative guide tries to go beyond the basics. It’s a good option for folks who want to get an understanding of various verbal sections and how to use advanced strategies to tackle verbal questions.