Hello BTG community. 
As I got lots of helpful tips from this board, I will let you briefly know about my experience with the GMAT.
I took the exam and am happy that I will hopefully never have to take it again.
My score: 740, Q45, V47.
Preparation material:
OG 12th edition
Indeed very helpful. If you want to score high, do not waste too much time with the easy questions, the ones towards the end are more difficult.
Powerscore Critical Reasoning Bible
Very helpful. Provides you with good frameworks that can help you solve difficult questions.
Manhattan Sentence Correction
Also very helpful, especially for me as a non native. Helps you to attack these questions systematically.
Kaplan GMAT Advanced
Not helpful. I did not work a lot with this book, but the questions I answered were not more difficult than the ones in the OG => In my opinion not worth the money, the OG in addition with the practice tests contains enough questions. In addition I hated their tipps: "An advanced test taker..."
Manhattan Number Properties
Also helpful, especially to improve your knowledge about integers (important for DS).
Manhattan Word Translations
Helpful, but not as much as the Manhattan Number Properties. The chapter on work problems is interesting, however.
My preparation:
I started in beginning of November, because I knew that I would not have any time to study during my exams period and Christmas. However, I only studied few hours at this time (the exam was soooo far away...)
Solved some sample questions in the OG and then after some days took GMATPrep1.
After this test and after all the others, I always analyzed my weaknesses. It was pretty obvious that my V scores were always below the Q scores, so I spend a bit more time on V questions.
What I recommend you: Also study concepts, not only practice questions! There are so many ways the GMAT can ask you questions, so it is useful to know how to attack a problem instead of only trying to remember a similar question.
Hope this helps a bit....
As I got lots of helpful tips from this board, I will let you briefly know about my experience with the GMAT.
I took the exam and am happy that I will hopefully never have to take it again.
My score: 740, Q45, V47.
Preparation material:
OG 12th edition
Indeed very helpful. If you want to score high, do not waste too much time with the easy questions, the ones towards the end are more difficult.
Powerscore Critical Reasoning Bible
Very helpful. Provides you with good frameworks that can help you solve difficult questions.
Manhattan Sentence Correction
Also very helpful, especially for me as a non native. Helps you to attack these questions systematically.
Kaplan GMAT Advanced
Not helpful. I did not work a lot with this book, but the questions I answered were not more difficult than the ones in the OG => In my opinion not worth the money, the OG in addition with the practice tests contains enough questions. In addition I hated their tipps: "An advanced test taker..."
Manhattan Number Properties
Also helpful, especially to improve your knowledge about integers (important for DS).
Manhattan Word Translations
Helpful, but not as much as the Manhattan Number Properties. The chapter on work problems is interesting, however.
My preparation:
I started in beginning of November, because I knew that I would not have any time to study during my exams period and Christmas. However, I only studied few hours at this time (the exam was soooo far away...)
Solved some sample questions in the OG and then after some days took GMATPrep1.
After this test and after all the others, I always analyzed my weaknesses. It was pretty obvious that my V scores were always below the Q scores, so I spend a bit more time on V questions.
What I recommend you: Also study concepts, not only practice questions! There are so many ways the GMAT can ask you questions, so it is useful to know how to attack a problem instead of only trying to remember a similar question.
Hope this helps a bit....
