The second edition of this book continues to provide a brief exposition of the principles of beam physics and particle accelerators with emphasis on numerical examples. It includes revisions and additions to every section with new material, figures, improved notation, and new or enhanced computer resources. There is also a reorganization of the contents and new sections. The latter include material on transfer maps, thermodynamics of beams, additional aspects of envelope matching, betatron resonances and dispersion with space charge, closed orbits, and beam cooling. The appendix has been completely reorganized, revised and updated and now includes short descriptions of the map code MaryLie, and the particle-in-cell code Warp.