This revised edition provides an up-to-date summary of the field of ultra-high energy cosmic rays, dealing with their origin, propagation, and composition,. The authors reflect the enormous strides made since the first edition in the realm of experimental work, in particular the use of vastly improved, more sensitive and precise detectors. The level remains introductory and pedagogical, suitable for students and researchers interested in moving into this exciting field. Throughout the text, the authors focus on giving an introductory overview of the key physics issues, followed by a clear and concise description of experimental approaches and current results.