MBA Entrance Exam

Hi Sowmya,
There is no best book for any subject out there. It all depends on how much you are practicing from it.
However, if I paraphrase your question, some of the most recommended books for MBA Preps are listed below, in order of priority for each subject:
Quantitative Ability:
Quantum CAT by Sarvesh Kumar Vwrma:
The book covers the basics really well and has a lot of practice sets of varying difficulty levels. The book is strongly recommended because of its simplicity, detailed solutions and mix of approaches.
Quantitative Ability for the CAT by Arun Sharma:
Pick this up if you have already completed Quantum CAT, or for some reason, not happy with it.
Verbal Ability:
Verbal Ability for the CAT Sujit Kumar
The most recommended VA book out there. Provides the most detailed solutions and the best approaches for VA in General.
Reading Comprehension for the CAT by Sujit Kumar
Again, probably the best CAT RC specific book out there. Detailed solutions and everything you need to learn the basics of RC Question Types.
RC99 by Aristotle Prep:
A GMAT Specific book containing 99 RCs divided into three difficulty levels ranging from Easy to Medium. Known for detailed analysis and solutions, this is the best book to continue practicing RCs from.
VA and RC for the CAT by Arun Sharma and Meenakshi Upadhyay Sharma:
Same as above.
Novels and Non Fiction:
However, the best way to improve your VA is to improve your comprehension and the best way to do that, is to read a lot.
If your question included the best Novels or Non Fiction Books that one should refer in order to master their reading skills, then I have shared a list of books on our FB Group, the link to this post is available at the bottom of this post.
Logical Reasoning and Data Interpretation:
While there are no LR/DI specific books that are recommended in general, the best way to master LR/DI is to refer Past Year CAT papers, Mocks, Previous Papers of Other Management Entrance Exams such as XAT, SNAP etc. You can also refer to our FB group where we frequently post LR/DI questions.
All the best.

It's good to see your awareness and seriousness towards cracking a management entrance exam so early. Still, in the first year, there is ample time for you. You can start improving your vocabulary by reading good novels/books and newspapers daily(especially the editorial columns). Solving some good logical puzzles and related questions will also help in keeping your mind fit and sharp. Nothing much needed to do for Maths, as of now. just ensure your basic concepts are strong. 1-1.5 hours is quite sufficient to prepare for the time being.
One important thing, there is absolutely no need to start a full-fledged preparation for CAT(or any other entrance exam) now. Focus the next three years on both enjoying your college life and studying well; this phase will never come back in life so make the most of it. Ensure you score well in your exams(it will prove very helpful afterward) and try building your profile by participating in college's extracurricular activities, certification courses or an internship if possible during vacations, social work, etc). Your profile will help you get that edge over others. All the best!