I think it is always best to read around the subject, and make your own choice, I am quite happy to believe in the old Irish legends, but Stuart Piggott's -'The Druids' has unpicked the stitches of the myths and legends that surround them. In the preface, the words 'Moonbeams from the Larger Lunacy' perhaps describes the historical evidence that evolved over the centuries. Hutton's 'Blood and Mistletoe' is another good read, never scoff until you read the evidence ;) The word 'Celts' of course has the same tones of disbelief as 'Druids' but that is another story....