There has been considerable progress in research into low-mass stars, brown dwarfs and extrasolar planets in the years since the first edition of this book was published in 2000. In this new edition the authors present a comprehensive review of both the astrophysical nature of individual red dwarf and brown dwarf stars and their collective statistical properties as an important Galactic stellar population. Chapters dealing with the observational properties of low-mass dwarfs, the stellar mass function and extrasolar planets have been completely revised. Other chapters have been updated, including important new material on observational techniques, stellar activity, the Galactic halo and field star surveys. The authors detail the many recent discoveries of new brown dwarfs and extrasolar planets and provide a state-of-the-art review of our current knowledge of very low-mass stars, brown dwarfs and extrasolar planets, including both the latest observational results and theoretical work.