Book excerpt: An introduction to evidence theory and its applications is presented in this book. It is based on the important Dempster-Shafer theory, which significantly generalizes classic Bayesian statistics and has proved to be useful in a variety of applications. The aim of the volume is to bring the theory up to date by focusing, in particular, on key work by Shafer and Logan as well as on some of the authors' own contributions. as: artificial intelligence, expert systems, information systems, computer science, decision making, problem solving, business management, statistics, and mathematics. This systematic self-contained description of evidence theory based on set theory is suitable for both lectures and self-study and should serve to strengthen the reader's background and problem-solving abilities.