the information received from bepposax, chandra and other instruments in the last two years has more than doubled the number of samples of gamma-ray bursts localized and followed up for afterglow search. this has also increased the interest of astronomers in grbs. this book reviews the research of the last two years and covers the global properties of grbs, grb afterglows, grb host galaxies, cosmology using grbs, and theories for grbs and their afterglows. theoretical and observational aspects are presented as well as tools for the analysis of the data.