I would want all book tips you could think of regarding problem solving and books in general, in elementary mathematics, with a certain flavour for "advanced problem solving". An example would be the books from [The Art of Problem Solving](https://www.newyorker.com/culture/persons-of-interest/richard-rusczyks-worldwide-math-camp), Arthur Engel's book and Paul Zeit's book. Books on certain topics, say geometry, are also appreciated!



Good books on problem solving / math olympiad
Polya's "How to Solve It" is a good one. When prepping for the Putnam, I used "Problem Solving Through Problems"


