Not a terrible book, but also not one that particularly excited me. The basic outline is that during the days of the Roman empire, a Vancian scoudrel type merchant character goes up from the Roman portions of Gaul and into the Gaullic portions of Gaul and then far beyond, trading, tricking, getting people killed, and in his adventures laying down the outlines of the Norse myths that we are familiar with today. While the book was decently written, it had a few issues that kept me from really enjoying it. These issues are mostly that Wotan wasn't more like Vance's Dying Earth series. The characters tend to be men of few words, and don't have the overblown and baroque rhetoric of Vance's characters. Rather they have a weird sort of pre-modern way of speaking and thinking, where motivation isn't always clear and there isn't a rich inner dialog. There will be actions, but only later if ever are the reasons for the actions clear. Another issue is that the balance between the main character and the world was off, equipoise was not maintained. With Cudgel in the Dying Earth, Cudgel's shittiness towards other people was always balanced by their shittiness towards him, e.g. Cugel might trick people and do bad deeds, but his deeds were always repayed in approximate proportion (and vice versa). Which goes a long way towards being able to enjoy and laugh at the story. It's Always Sunny has a similar balance, and it's the only thing that makes these sorts of comic Chaotic Evil characters bearable, that their schemes injure themselves as often as other people. In Wotan the balance is off, and while the main character suffers somewhat, it's not proportionate to what he causes to happen to other people. Which makes it difficult to sympathize with him and laugh at his adventures, and makes it more difficult to ignore the problematic parts of the story.
A final issue I had was that while I get what the author was doing (provide a potential origin for Norse myths through realistic actions and events), it just didn't do much for me. I'm not super into Norse mythology, and I didn't find the author's origin-seeds to be particularly clever. There is an additional weird/interesting thing going on, that while Wotan is laying down a realistic basis for the Norse myths that we have today, the story also has super-natural elements in that there is an actual Greek-God driving Wotan's actions. So it's a Myth-Realism-Myth sandwhich. Which might have been tastier to me, except that the underlying myth starts getting into the noble and tragic destiny of the German people and their martial spirit (and mentions the battle of Jutland?), which is like ehhhhhh. Not necessarily Nazi but again not really my area of interest.
Anyway! It's a competent book, but not particularly engrossing and it took me ~2 weeks to read 200 pages of it in bits and bursts. There was another 400 pages to go and I decided to opt out of that experience when I came to the end of the first story-part.