Short answer: Buy according to your board and school, not according to what looks popular. Each board follows its own books and syllabus.
CBSE
CBSE schools largely follow NCERT textbooks, with reference books chosen by each school.
ICSE and ISC
ICSE schools generally prescribe books from specific publishers. Ask for the school list before buying.
State boards
State boards publish their own textbooks, often in more than one language. Make sure you buy the right medium and year.
Avoid wrong purchases
Take the book list from your school, match title, author and edition, and ask the seller if the listing is not clear.
Frequently asked questions
Can I use CBSE books for a state board exam?
Not as a substitute for the prescribed books. They may help as extra reference, but follow your board syllabus.
What if my school list changes?
Wait for the final list from your school before buying everything, especially for reference books.