Well, to be very honest, NO. GMAT Official Guide is very good but not good enough. If your aim is to really score 720+ on the GMAT Exam, preparing only from the GMAT Official Guide will not suffice. You will have to refer to a lot of other books and not just books, lots of other material (forums, channels, blogs, etc...) before you can safely say that you are adequately prepared for the GMAT Exam.
Some of the books and material that you should refer to adequately prepare for the GMAT Exam are as follows:-
- GMAT Official Guide
- GMAT Quantitative Review
- GMAT Verbal Review
- Manhattan Prep Books
- Veritas Prep Books
- QDS Pro Coaching Class Study Material
- GMAT Club Blog
- YouTube GMAT Prep Videos
Practise from as much material as possible, from as many sources as possible. The more you practice, the better you become !