The fourth 86 novel continues from where the Anime adaptation concluded. And aside from some early personality differences (which eventually clear up) it’s a pretty smooth transition.
Content-wise it decides to offer a brief interlude from the horrors of war to focus on the mutual dehumanization the Republic and 86 engage in (the latter as a defense mechanism). But only at the surface level; the actual cause of the Republic’s sudden suicidality genocidal policies is not mentioned. I’m wondering now if it actually was revealed in the earlier novels and just cut from the adaptation. That seems like a weird oversight to have made though.
Regardless, the fifth book then returns to the topic of ruinous battlefield horrors while simultaneously giving us a look at another of the surviving countries fighting off the Legion. It also happens to feature some welcome character development for both Shin and Anju. All-in-all ending up both a solid self-contained story arc and continuation of the series’ core plotlines.