By Juliet Marillier. Book one of the Bridei Chronicles.
I think my focus in reading these may have changed from reading some of Martin LaBar's reviews (here and here, among others), and definitely from reading The Heavenly Man.
"They built high places for Baal in the Valley of Ben Hinnom to sacrifice their sons and daughters to Molech, thought I never commanded, nor did it enter my mind, that they should do such a detestable thing and so make Judah sin." (Jeremiah 32:35)
Not many authors seem bold enough to make one of their main characters a cold-blooded murderer. This is absolutely the most horrifying of Marillier's books, and since she says in the author's note that she devised the religion herself, there seems to be no good reason to include such an abomination in her story, much less have the focal point of the whole series (assuming "The Bridei Chronicles" is an accurate predictor) participate in it.
The people in this book have hardened their hearts against God. A major part of the story is about how the kingdom has split because of the Christian influence coming into the south; the chieftans of the north refused to recognize a king who abandoned their pagan faith. In the book, men died in battle only to retrieve a standing stone, a gesture that is depicted as valiant and greatly symbolic in the book even though the stone is in effect a worthless idol. (Someone can probably quibble here that they don't actually worship the stone, but...)
The characters struck me as being paragons of their type; each one is exceptional in whatever he does: Broichan, the perfect druid; Donal, the perfect warrior; Faolan, the perfect spy, etc. Even Tuala, though I found myself sympathetic with her, seems to be the perfect student, although she is led astray by the interference of the so-called "Good Folk."
The scenes with the two "Good Folk" are another source of irritation to me; I think they could have just as easily been left out for the reader to imagine, or not. Having two characters who seem to be almost omniscient in a way drop hints before the story is revealed made them even less likeable than they already were. The scary part is, they barely seem to understand humans and act like the whole thing is just a game.
A well-written book, despite the perhaps confusing nature of the genealogies, but you could easily find a better story.