This review will contain some spoilers for the previous Overlord light novels.
The Men in the Kingdom Part 1 is a bit tricky to review since it is only half a story. By and large, this book feels more like it is just getting things ready for the next one. While it is true that nothing too crazy happens, there are some other key points to the novel. Aside from the set-up for Part II, this story does a lot for world building and character development in Overlord.
It has been clearly established that Ainz and his minions are all-powerful compared to the other inhabitants of this world. If their goal was simply to raze everything to the ground they could do so, easily. But Ainz works on the assumption that there are powers that could threaten them in this world. To that end he attempts to gather information and that sets up our world-building. This novel focuses on Sebas and Solution gathering information in the capital city of the nearest country. Their actions allow us readers to see what everyday life is like in this world for human civilians.
World-building and character development are a bit linked here, with a few regular human characters introduced. We meet the princess of the kingdom, her loyal bodyguard, one of the few groups of the highest-ranking adventurers, and revisit Brain (the warrior who fought Shalltear in volume 3). For the main characters, this book focuses on Sebas. Seeing each of Ainz’s top people get their own story is fantastic; many other series would just turn at least some of them into background characters. Sebas himself is also interesting because he is one of the inherently good denizens of Nazarick. He will follow his orders, but will also try to do the honorable thing within the boundaries of those orders.
Overall this book was enjoyable, but again it is only half of a story. The stopping point for this novel did feel pretty good. There is a little bit of a cliffhanger to tease audiences, but it is done in a fun way. Given how much this book felt like set-up, Men in the Kingdom Part II will probably be action packed. That is not to say it is not interesting to see the characters maneuver through politics as well as battlefields. And there is a bit of fighting in this book, just nothing over the top. But Men in the Kingdom Part I definitely gives the sense that there is a greater battle to come.