In competitive programming I believe every programmer has his/her favorite books (or blogs or reading materials) from which s/he learns(or learned or is learning) a lot. According to your opinion what are the best learning materials in your CP life and you would suggest as a programmer to another programmer must to read.

Thank you. Happy Learning !!!

[Although I am not so much experienced but I have some favorites and one of them I think, "Competitive Programming 3 by Steven & Felix.]