i m nt taking any coaching fr cat i m doing self study n i m a 3rd yr student wht books shuld i refer fr my better study

Arun Sharma right now is the best Author for the CAT preperation.You do not really need to solve each and every sum in all of those Arun Sharma books.
Apart from that, here are some books you can practise from -
Quantitative Aptitude:::
For this go for How to Prepare for Quantitative Aptitude for CAT by Arun Sharma
More than the number of questions you will practice more used to you will get of it. Focus on how you can tackle a question with the bare minimal calculation. Most problems in CAT/GMAT are actually meant to test your ability to look at a complex scenario and find simple solutions to it.
Data Interpretation & Logical Reasoning :::
How to Prepare for Logical Reasoning for the CAT by Arun Sharma
How to Prepare for Data Interpretation for the Cat by Arun Sharma
Verbal Ability and Reading comprehension :::
Read a lot of english novels and editorials from daily newpaper, I'll say go with THE HINDU, just read it daily and you will notice the difference yourself.
One of the best currently present, if you wish, go with
Word Power Made Easy Book by Norman Lewis

ALL THE BEST FOR YOUR FUTURE!!