+1 for Proofs from the BOOK, Visual Group Theory, and Flatland, already recommended by others. -1 for Polya's How to Solve it - I don't remember a damned thing

+1 for Proofs from the BOOK, Visual Group Theory, and Flatland, already recommended by others. -1 for Polya's How to Solve it - I don't remember a damned thing from it.