As the most compact known observable form of matter, neutron stars offer a fascinating range of problems to astrophysicists. This book offers a collection of reviews of current research on neutron stars, variously observed as radio pulsars, X-ray binaries, gamma-ray sources and sources of thermal X-ray emission. The reviews are meant for an audience of graduate students and scientists in the field, so they combine a tutorial approach with the objectives of a scientific review. The central theme of the book is evolution, stressing the changes of thermal, magnetic and dynamical properties throughout the lives of neutron stars.