Where did the Celts come from?

[Ranika]

I find Barry Cunliffe often has great insight into the early Celtic world, and Powell as well. If you're more concerned with disinformation and wading through misconception, a great book is The Celts - Origins, Myths and Inventions, which is by John Collis.

Edit; I think it's John Collis. I'm sure PyschoV has the book, he'd know the author. I'm fairly sure it's Collis.