James L. Nelson is a very good writer. As an ardent fan of Bernard Cornwell and Steven Pressfield, it's a high bar a historical novelist has to meet to gain my praise. I put JLN in that august company.
As a lifelong historian and historical warfare reenactor and competition fighter, I'm a hard audience to please. I know what fighting in armor feels like. I know the history, and get easily "irked" when authors get it wrong.
That said, Nelson got it mostly right.
He creates a believable and historically accurate backdrop and fleshes it out with equally believable (for the most part) characters. His protagonist, Thorgrim Nightwolf, is both a verifiable badass and three dimensional human being with understandable emotions. Fin Gall is a good story. It is well paced, complex enough to keep one guessing, and has a satisfying ending. The villains of the piece are dispicable while not being cardboard-cutouts.
When it comes to the scenes at sea, Nelson is right in his wheelhouse. A former mariner (apparently), he has a feel for the sea, and I could feel the Viking ship under my feet as I read his prose.
That is the good.
Why I gave Fin Gall only 4 stars out of 5 is a few (very) minor points regarding combat, weapons, and armor of the period.
First, Nelson has the Irish high-born leaders wearing mail. BIG historical mistake. The Irish did not wear armor in the Viking Age. It is telling that they could tell the "Gall" from Irish forces at a distance by the fact that the Danes and Norse wore mail! Famously during the closing minutes of the Battle of Clontarf, King Brian Boru was told by his lone bodyguard that men in the distance were approaching his tent. Brian asked the guard what they looked like. “Blue and naked men”, came the response. “They are Danes in their armor”, exclaimed the king! From the distance chain mail gave the wearer a blue appearance. It was the fact that they were wearing mail that distinguished these warriors as Vikings, as no Irish warriors wore mail.
The second nitpicky point is that in every combat Nelson has his warriors primarily thrusting with their swords. While the point was sometimes used, Viking and Irish swords of the period were primarily slashing/hacking weapons. Not a big point, but it bothered me that the author didn't do his research.
Finally, in one battle the Irish mounted troops are depicted as mailed horsemen charging with lance. I've already noted that the Irish didn't wear mail. The Irish also never used cavalry in the shock role: well-born warriors might right to battle, but dismounted to fight. Nor did the Irish (or Vikings for that matter) have any lance-armed horsemen. The main weapon of the Irish was the javelin, light spear, or by the 10 century the Dal Cais ax.
All this is not to say that these ahistorical points ruined what was a very good historical novel. In fact, I enjoyed it immensely and ordered the second in the series. But if you are an aficionado of Dark Ages warfare, you might be bothered by these small points as much as I was.
Final word: Deadliest Warrior recommends you buy this book. I am hooked, and looking forward to reading the next in the series.