This app was mentioned in 2 comments, with an average of 2.00 upvotes
For ncert textbooks, there's an app on playstore.
https://play.google.com/store/apps/details?id=com.ncert
And for rs aggarwal maths,
You just need an app for it. https://play.google.com/store/apps/details?id=com.ncert&hl=en