This set of academic papers from a conference considering, from archaeological, linguistic, and genetic viewpoints, the question of who the Celts were and where they came from, has been assembled into a beautifully illustrated book. While more scholarly than a work aimed at the general public, it is certainly accessible, with clearly made points and unobtrusive footnotes. So far I have only read in full the three chapters on genetics. One is an article by a researcher with the People of the British Isles study, which helpfully begins with an overview of how DNA works, before surveying what studies have found, or at least asserted, about European DNA in general and British DNA in particular. Next is a summary of DNA research about Ireland, by the leading researchers McEvoy and Bradley. It includes an explanation of the Y-DNA "Irish Modal Haplotype." Third is a very welcome summary by Stephen Oppenheimer, author of The Origins of the British: A Genetic Detective Story, in which he responds to criticisms of his groundbreaking research. The most important part of the linguistic section must be John T. Koch's finding that the language of Tartessos in ancient Iberia belongs to the Celtic group. The proof of that brilliant finding is exhaustive, even if it is beyond the comprehension of readers who are not linguists. Readers who like Celtic things and are satisfied just to get a tattoo and wear some plaid with swirly silver jewellery should probably avoid this book; on the other hand, this book is must reading for those who really want to know what the Celtic world was all about.