Research on extrasolar planets is one of the most exciting fields of activity in astrophysics. In a decade only, a huge step forward has been made from the early speculations on the existence of planets orbiting "e;other stars"e; to the first discoveries and to the characterization of extrasolar planets. This breakthrough is the result of a growing interest of a large community of researchers as well as the development of a wide range of new observational techniques and facilities.Based on their lectures given at the 31st Saas-Fee Advanced Course, Andreas Quirrenbach, Tristan Guillot and Pat Cassen have written up up-to-date comprehensive lecture notes on the "e;Detection and Characterization of Extrasolar Planets"e;, "e;Physics of Substellar Objects Interiors, Atmospheres, Evolution"e; and "e;Protostellar Disks and Planet Formation"e;. This book will serve graduate students, lecturers and scientists entering the field of extrasolar planets as detailed and comprehensive introduction.