While I do not consider this to be one of the greatest books I've ever read, it certainly is a good one. It has it's flaws, yes. Every book does.
I was a little surprised that Llywelyn actually included human sacrifice in her portrayal of the druids, considering that the only source of "witness" to such practices were the Romans themselves, who, being the enemy of the Gallic Celts, were known to create various lies to plant fear of the druids in the minds of their followers. Note that I am not deducting any stars due to this, though, because there is very little we know about the Celts and their lives and one cannot be absolutely certain.
However, I feel the need to defend this book against some of the reviews, because, frankly, many of them were down-right stupid.
Take, for instance, the reviewer who deducted a star merely because it had a "sad ending". How many books have sad endings? Some of the greatest books of all time do! It has nothing to do with the quality of the book, so don't deduct from the average star review for such a stupid thing as that! He follows up with an "Oh, well, that's history" attitude. So why deduct the star at all?
Oh, and the person who complains about the central character being "egotistical"...So what if he ever showed any signs of egotism? That's his character! Once again, that's a part of the story. And then you spoke of the Romans being "exaggerated". That's because it was from the Gallic Celts' point of view. Of course they're going to portray the Romans that way! It's their point of view! Oh, and if you're going to bash a book, at least use something resembling good English grammar so you don't look like a complete fool. There's a difference between typos and not using anything resembling capitalization, punctuation, etc. When talking about the Romans, use the plural form of the word. "of Roman" does not cut it.
And there was another man who said the characters were too "sophisticated" for him, because the Celts are shrouded in such mystery. You're right, there is much we do not know. But the author has the license to guess. She seems to have done a fairly good job at remaining as historically accurate as possible. What do you want her to do? Have paper-thin, 2-dimensional characters? Come on! She has to breathe life into them somehow! And there is hardly a reason to believe that the Celts didn't have the vocabulary to express concepts such as "professional jealousy."
Sorry for ranting like this, but I'm tired of stupid, trivial reviews complaining about stupid things. Reviews such as "this isn't what I was looking for", so the book itself is terrible because "I was unaware of its true content".
Like I said, this wasn't a perfect book. I give it four stars because I believe it deserves that much for it's fluidity and presentation. It reads pretty well. But it lacks something.