Hi JayMekk,
As bb's already mentioned, you should take one of the free practice CATs available from GMAT. There's really no better way to assess your skills, strengths and weaknesses than by taking a FULL CAT (with the Essay and IR sections) under realistic conditions. While doing questions out of a book can help you to train and hone your skills, that process doesn't really compare to taking the full adaptive GMAT in one sitting. Once you have your scores, you should report back here.
1) What is your goal score?
2) When are you planning to take the GMAT?
3) When are you planning to apply to Business School?
GMAT assassins aren't born, they're made,
Rich