I had never read a Viking-noir saga before "Downfall," but I think I like it.
The book features Finn Styrrsson, a Viking with the strength of thirty men [sic] in each hand who travels the world slaying monsters with the hope of a glorious death that will see him to Valhalla.
I like that the book has a consistent voice, and it's not a voice that I'm used to hearing. Unruh brings together Norse mythology, modern language, and an enjoyable protagonist with few seams. Finn is compelling -- I care about his mission even though his Viking values have very little that is connected to my own, and I believe that he has the voice of a berserker. I also enjoyed the bits of cunning and political diplomacy mixed in. In that sense, it was very much like a modern (and Norse) version of "The Odyssey." Also, I am used to tolerating books with unassuming beginnings that pick up a few chapters in, but "Downfall" captivates from the start with a superb first page and first chapter.
Stylistically, my one main issue with the book is that some of the fights are so epic as to be unimaginable. I can suspend disbelief that the protagonist is mythically strong, but it often seems like, at the start of a battle, the enemy is literally the size of a house, and midway through, Finn is able to throttle its neck (which would be moderately impossible with something that big).
Also, I was reading an ARC, so more editing will be done before it is published, and this critique is totally unfair, but I felt that the writing lacked a certain meticulous quality. There were a few sentences interspersed throughout the book that I would have to read twice to completely understand because they were slightly less clear or more ambiguous than they should have been, which is something that you can only really get rid of by spending a very long time editing everything.
While it was an enjoyable read, I didn't feel like I gained any insight into the human condition from reading it, an expectation I hold even of fantasy works. As a result, it only gets 4 stars rather than 5, but if you're looking for a fun Viking novel, I strongly recommend it.