I like how slavery is tackled here. It shows that Yukimura brings more to the table than a skin-deep level understanding of the problem. It's not all about "ugh, slavery is just bad and tragic because you get whipped by your master".
We get to see some more intricate power dynamics at work between different groups of disenfranchised people competing with one another for limited resources. We can assume how they could possibly arrive at this kind of antagonistic mindset and how it keeps them in line.
The character of the master is interesting. He's not some sort of a stereotypically sadistic psychopath. Instead he's written to be a man who can gaze upon his idyllic land and even go and blithely mingle with his serfs and keep up the pretence of benevolence, because he's not the one who directly manages his estate. He doesn't even need to intervene that much in anything, doesn't need to get his hands dirty, because the poor oppress each other well enough on their own. That's a pretty satisfactory depiction of internalised exploitation to me.
Also, on the level of imagery, I like how Yukimura takes some time to actually show the toil and the physical exhaustion that is the main part of a slave's life. This kind of dedication to depicting the mundane realities of every-day existence, the ordinary day's plight, was something I missed in the war arc.
War arc was by and large a story about prevalent violence of the period, but there wasn't actually that much gore. Yukimura made one of the main characters a jaded type with a superiority complex who admits he despises Vikings for their crude brutality among other things, but then we actually didn't get to see that much of the said brutality explicitly. When a village gets pacified, you realise that it's bad and reprehensible, but the event is not represented as some sort of a Dantean horror scene that would truly drive home the point that perhaps Vikings are not so cool.
Imo, this kind of rather timid representation of Vikings' violence makes it far too easy to move on and continue to enjoy their bloody adventures without much cognitive dissonance. It's what makes it possible to find Thorkell's warmongering amusing. "Oh, they pillage villages, they terrorise the civilians, but they're Vikings after all, that's what they do, such were the times".
So it's good to see that Yukimura is concerned with depicting slavery and exploitation realistically. It feels like Thorfinn's slavery will be an honest exploration of the topic rather than a mere "fall from grace" episode.
(Edit: Well, all of these concerns get pretty much resolved in the next volume, though xD)