Hi Rohitesh,
There are a variety of different resources that you could use during your GMAT studies. Most Test Takers use a combination of resources, but those who take a 'book-heavy' approach often get 'stuck' at a particular scoring level. Thus, to hit a 700+ score goal, you'll likely need to invest in more than just a series of GMAT books.
It sounds like you're just starting out. Is that true? Have you done any studying so far?
If you're just beginning, then it would be a good idea to take a FULL-LENGTH practice CAT Test; you can download 2 for free from
www.mba.com (and they come with some additional practice materials). A FULL CAT takes about 4 hours to complete, so make sure that you've set aside enough time to take it in one sitting. Once you have those scores, you should report back here and we can come up with a study plan.
GMAT assassins aren't born, they're made,
Rich