This volume reviews recent research progress in the field of quasar absorption line systems, from both observational and theoretical perspectives. The seventy-eight papers cover topics ranging from the galaxy-absorber connection, Lyman-alpha systems, abundances and dust, and high redshift studies including re-ionisation, to models and numerical simulations concerning many of these aspects. The papers include detailed reviews by leading researchers in these fields as well as many new results reported here for the first time, and provide a valuable resource for graduate students and professional astronomers.