Hello,

Look it's totally depends on you and your institution. If any institution increase you to buy a particular book because they are following these book then you have to buy. If you have any problem then you will directly talk to the institution authority. There are no mandatory for any examination that you have to read only one particular book. For JEE mains and NEET so many good books are available. Which one is suitable for you, you can read it. And NCERT books are also available. So better you can talk to your institution authority.

All the best.