1. NCERT Mathematics Textbook for Class IX [NCF – 2005] is fantastic book as itt touches nearly all topics (like geometry, polynomials, Number Theory (rational – irrational numbers), Introduction to mathematical modelling).FOR EXAMPLE: I was spell bound by chapter – “Introduction to Euclid’s Axioms” and I ended up reading “Euclid’s Window by Leonard Mlodinow “ & “Fun & Fundamentals of Mathematics by Narlikar
2. NCERT Mathematics Textbook for Class X [NCF – 2005] also consists of basics of “Number Theory” topics like “Euclid’s division algorithm”. Moreover the appendices on “Proofs in Mathematics” & “Mathematical Modelling” are worth reading even at later stages. FOR EXAMPLE: The discussion on ‘Proof by Contradiction’ is awesome.
3. NCERT Mathematics Textbook for Class XI[NCF – 2005] includes some of most fundamental mathematics concepts like “Set Theory”, “Principle of Mathematical Induction”, “Summation of Series”, “Binomial Theorem” & “Permutation & Combinations”. Also appendices on “Infinite Series” & “Mathematical Modelling” are worth reading.
4. NCERT Mathematics Textbook for Class XII [NCF – 2005] major focus in on Calculus, but still its appendices on “Proofs in Mathematics” & “Mathematical Modelling” are worth reading. FOR EXAMPLE: In Appendix – 1 (Proofs in Mathematics), there are proofs for two beautiful theorems of Number theory (a) Prime Numbers are infinite & (b) Fermat Numbers are NOT Prime

These NCERT textbooks were written before 2005, they still follow the old notation to represent natural numbers, integers etc., for example: using  N instead of   to represent set of natural numbers.  Since, only after 2003, bold font (like N)  was completely replaced by  blackboard bold font (like  ) to represent some familiar systems of numbers (like “set of natural numbers”) in print.

[Last Edited: 19 December 2015]