This book was the fruit of the joint work of the most famous Celtic scientists, Miles Dillon and Nora Chadwick. This is a generalizing and in some way summarizing work, containing all the most important data and information collected by Celtology by the mid-60s of the XX century. Along with the broadest coverage of the material, the great merit of this book is the truly scientific approach of the authors, who base their presentation only on reliable and verified information, scrupulous and thorough analysis and comparison of sources.