XAT

Some reference books are not enough, if you're studying for MAT or GMAT especially on your own that is. Firstly, if you're studying on your own, make sure that you spend at least 6 hours a day with at least 4-6 months of determined attention towards your studies. Secondly, there are a lot of YouTube tutorials on the Internet that'll help you do the right kind of preparation and keeping the schedule. Finally, coaching for these exams separately or altogether will cost you a lot, so keep that in mind and fuel that as your passion. If you can study this way, you can make a difference. So don't just go by some reference book by the market. There are hundreds of books, plan your schedule properly and use technology along with your studies. Good luck and all the best for your future endeavours.

GMAT preparation books:
Veritas Prep Complete GMAT Course Set
The Complete GMAT Strategy Guide Set by Manhattan Prep
The Official Guide to the GMAT Review 2018
MAT and XAT preparation books -
How to Prepare for Quantitative Aptitude for the CAT by Arun Sharma (Published by McGraw Hill)
How to Prepare for Data Interpretation for CAT by Arun Sharma (Published by McGraw Hill)
Logical Reasoning and Data Interpretation for the CAT by Nishit K Sinha (Published by Pearson)
How to Prepare for Logical Reasoning for the CAT by Arun Sharma (Published by McGraw Hill)
Logical Reasoning and Data Interpretation for the CAT by Nishit K Sinha (Published by Pearson)
How to Prepare for Verbal Ability and Reading Comprehension for CAT-by Arun Sharma & Meenakshi Upadhyay.