The book "Discrete Mathematics" by Jean Gallier provides a comprehensive introduction to discrete mathematics, particularly aimed at students of mathematics and computer science. It begins with the fundamental rules of mathematical logic and offers numerous examples of formal and informal proofs. With a solid logical foundation, the book covers the essential axioms of set theory and introduces natural numbers. The subsequent chapters focus on functions and relations, directed and undirected graphs, as well as an introduction to combinatorics. Special attention is given to public key cryptography and the RSA algorithm, including complete proofs of Fermat's little theorem and the correctness of the RSA scheme. The book is richly illustrated and concludes each chapter with a list of problems of varying difficulty levels.