Books/Study Material
Section wise books I recommend
Puzzles:
Mathematical Puzzles: A Connoisseur's Collection - by Peter Winkler
Entertaining Mathematical Puzzles - by Martin Gardner
Mathematical Puzzles of Sam Loyd
Algorithms:
Introduction To Algorithms - by Cormen, Lieserson, Rivest
Algorithms - by Robert Sedgewick
C++:
C++: The Complete Reference
The C++ Programming Language - by Stroustrup
Programming in C++ - by Cohoon and Davidson
Probability:
Probability, Random Variables And Stochastic Processes - by Papoulis
Fifty Challenging Problems in Probability with Solutions
Engineering Mathematics:
Advanced Engineering Mathematics - by Kreyszig
Linear Algebra And Its Applications - by Gilbert Strang
What Is Mathematics? - by Richard Courant
Quant Finance:
The Quants - by Scott Patterson
My Life as a Quant: Reflections on Physics and Finance
Fooled by Randomness: The Hidden Role of Chance in life and in the Markets
Beat the Dealer: A Winning Strategy for the Game of Twenty-One - by Thorpe
(Disclaimer: I get affiliate revenue from flipkart if you buy these books from flipkart through these links)
Some math links I follow
Gurmeet Singh Manku's Blog
CMU - The Puzzle Toad
IBM Ponder This
William Wu's Collection
C Puzzles by Gowri Kumar
Rustan Lieno Collection
cotpi
A Puzzle Blog
Me, Myself and Mathematics
A Wanderer
Nicks's Mathematical Puzzles
Gowers's Blog
Tanya Khovanova’s Math Blog
in theory
The Math Less Travelled
Wild About Math!
Terry Tao
A Computer Scientist in a Business School
Combinatorics and more
A Neighbourhood of Infinity