On the one hand, it is not actually a bad read for a sword (not much sorcery) novel, but it has some real problems with fidelity to Robert E. Howard's Conan. In fact, if you can forget it's supposed to be a Conan prequel, it works okay. However, as a tale of the sword swinging barbarian, it has quite a few holes.
The story takes place before the first of Robert E. Howard's tales, though he did allude to the Aquilonian outpost of Venarium, which was overcome by Conan and his people. Turtledove faces a problem: how to allow the Aquilonians to establish Venarium in Cimmeria and to keep it standing? The Cimmerians of the Conan saga don't come across as meek or submissive. I imagine something akin to Fort Tuscelan's struggle for survival in Howard's Beyond the Black River.
For me, Turtledove does not pull it off very well. The way Venarium is founded and the Cimmerian response is not at all what I depict. Regarding Conan's home village, Duthil: it comes across as your standard medieval village. There houses with several rooms, shops, a main street: this does not remotely strike one as a barbarian community. And we're at the root of the problem. An unlikely premise (the way Venarium was established) and an unbelievable depiction of Cimmeria. It's going to be hard to win over a knowledgeable Conan fan after this start.
A Conan tale with what I believe to be a much more realistic portrayal of Howard's vision is John Maddox Roberts' Conan the Valorous. Further, the Conan Role Playing Game supplement, Cimmeria, presents a more palatable view of the land and how the people lived.
The attitudes of the Cimmerians seem awfully civilized for a nation of, well, you know, barbarians. In fact, again, it seems rather medieval. To his credit, one thing Turtledove does well is incorporate the Aquilonian soldiers into the story. Their scenes give some depth to the tale. This is offset somewhat by the stereotypical bad guy: in this case, Count Stercus. He is about as deep as Snidely Whiplash.
The last chapter shifts to a tongue-in-cheek style, a tone completely out of place with the entire book. It is just about as silly as the chapter titled, "The Temple Out of Time," which does not remotely fit into the story. I haven't read all of the Conan books yet, but this is the first I've come across with no sex. Perhaps not surprising, since he's only 15 at the end of the tale, but it is another uncharacteristic element of the book.
While this seems like a pretty negative review, I didn't mind reading this book: it just isn't an authentic Conan tale. It reminds me of Quinn Fawcett's Mycroft Holmes novels. They were nice Victorian-Era James Bondish books: they just weren't Mycroft Holmes. In case you don't know, Mycroft was Sherlock Holmes' smarter, older brother and not at all a secret agent type of guy.
But I hoped for a better Conan coming-of-age tale. Since the copyright holders of Conan are inflexible regarding official pastiches (non-Howard tales), it is unlikely anyone will be given permission to tell the Venarium story again. Hopefully an unauthorized attempt will succeed where this one failed. And I'll add that I very much enjoyed Turtledove's alternate-Civil War history book, The Guns of the South. Just not this Conan novel.