I will have to disagree with Arun. I think it really depends on how good you are with your basic grammar knowledge. I think what Arun is saying is you dont have to be a master in grammar to crack GMAT instead need a better understanding of what the sentence is trying to say and see if it really says what it is trying to say. I agree with him on that, however, my problem is you wont be able to get the true meaning of a sentence if you dont have basic grammar knowledge.
Its very easy to say subject and verb must agree. But whats tricky most of the time is to find out what the subject and verb actully are...
So, Long story short, I would certainly say go to Wren and Martin but dont go from page 1 to the end of the book. That is not an efficient way of doing it. What I would do is find what are my weak areas. For example, if I am having diffficulty in determining how a clause modifies the subject then I would go check out the chapters pertaining to clauses from wren and martin, do all the excercises in those chapters and so on.
Use wren and martin as a refrence when you need it rather than a GMAT study material so to speak. A lot of the time GMAT prep material will assume that you know the basics and that is the time where I would refer to wren and martin. Ex: it may say a subject in this sentence is X and not Y and you may not know why X is subject and not Y. If you are in that kind of situation then you certainly need a good grammar reference book and I think wren and martin is the best grammar book for the basics.
Also: Check this out:(I know you said DO NOT SUGGESt other books)
I think this is a great website if you want to nail your basics. it has plent of example to follow and is makes you practice practice practice:http://lessons.englishgrammar101.com/En ... eword.aspx
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