At the moment, Amazon's page for this book has no description or table of contents, but I can tell you it consists of almost all the academic papers presented at this conference: [...] , along with an excellent introduction.
These are densely written evaluations of the archaeological and linguistic clues as to who the Celts were. It is a slow read for any non-specialist; for example, a 21 page essay with an eight and a half page bibliography includes sentences like "The contextual reliability of some of the early 5th millennium BC metalworking dates has been questioned recently (Roberts 2009, 470), such as those from Cerro Virtud in south-east Spain (Montero & Ruiz Taboada 1996; Delibes de Castro & Montero 1999; Ruiz Taboada & Montero 1999; Montero 2005), and Cabezo Juré in south-west Spain (Nocete 2006)." But that is how academics make the careful and cautious arguments that advance the state of knowledge in the social sciences. So if you like the challenge of thinking hard about such things, this is great stuff. About 68 maps and illustrations, many in full colour.