Sentence Correction GMAT Preparation Guide (Manhattan GMAT Preparation Guides)

This is the greatest book explaining all underlying rules for GMAT Sentence Correction among the books I used to prepare for GMAT. It provides very in-depth but easy-to-understand explanations for almost all aspects of English tested on GMAT.
The only reason why I was slightly disappointed with this product was examples and problem sets. It looks like they were not proof-read and thus they are inconsistent with the grammar rules described in the corresponding chapter.
So my advice would be - buy this book, use it as your primary grammar guide, but don't be too much concerned with the problem sets and explanations on the correct answers.

Finding it extremely helpful for my GMAT prep. Stresses on the grammar basics with good examples. The downside is you have to buy the GMAT official or Verbal book for exercises, manhattan standalone does not have many exercises for you to practise.

This is the best book for sentence correction, specially if English is your second language. Provides a great overview of important concepts, a grammar exercise on each topic and then points to a bunch of relevant questions in the Official Guide and GMAT Verbal review.

If you don't want to be at a serious competitive disadvantage or if you are not already god at SC, my advice is that buy this book as early as you can in your GMAT preparation period.