How to Solve It: A New Aspect of Mathematical Method
by George Pólya
Classic problem-solving text teaching systematic heuristic methods for mathematical problem-solving applicable across disciplines and life.
More resources on Logic
Gödel, Escher, Bach: An Eternal Golden Braid
Pulitzer Prize-winning exploration of consciousness, artificial intelligence, and meaning through connections between mathematics, art, music, and formal systems.
Book of Proof
Essential introduction to mathematical proof techniques covering logic, sets, relations, functions, and various proof methods for pure mathematics.
Discrete Math Textbook (free PDF)
Oscar Levin's free discrete math book with logic chapter
ProofWiki
Comprehensive wiki for mathematical proofs and logic
Modal Logic
Explore modal logic with Prof. Yablo's MIT course! Learn about necessity, possibility, and reasoning with possible worlds.
Logic II
Explore advanced logic with Prof. Vann McGee's Logic II course. Delve into model theory, incompleteness, and more.