I can't really say for sure as I haven't read volume 15. But in previous volumes, we've seen characters like Ainz grow in terms of his understanding of the new world and his leadership skills.
If we consider the pattern from earlier volumes, in volume 15, characters might become more complex. For example, side characters could gain more depth in their personalities. Maybe some characters who were once just followers start to have their own agendas. However, this is just a guess based on how character development has been in the past in Overlord.
Character development in Overlord has been gradual. In volume 15, it could be that characters face moral dilemmas that further shape them. For instance, if Ainz has to make a difficult decision that goes against his original beliefs from when he was just a player, it would be a significant step in his character development. But again, this is all speculation without having read the volume.
It could be more in - depth. As the story progresses, characters usually grow. Maybe the Shield Hero becomes even wiser or more powerful in volume 6 compared to before.
It could have a more complex plot. Maybe it builds on the events of the previous volumes and takes the story in a new direction.
Compared to the previous volumes, Volume 14 could introduce new elements to the world of Mushoku Tensei. It might expand on the magic system or introduce new races. In terms of the writing style, it could be more refined as the author has had more practice by the time of writing this volume. Also, the relationships between characters may have evolved in more intricate ways.
Volume 17 might have a more complex plot compared to the earlier ones. As the story has been building up, this volume could have more intertwined storylines.
It might have a more advanced plot. The story could be more complex compared to the previous volumes as the characters have already been established in earlier installments.
In volume 5, it may build on the foundation laid by the previous volumes. The world - building that started in earlier volumes might be expanded further. We might see more of the consequences of the actions taken in previous volumes. For example, if the protagonist made certain decisions in volume 4, volume 5 could show how those decisions affected not only him but also the other characters and the world around them. The character development might also be more advanced. Characters who were relatively one - dimensional in the beginning might have become more complex and multi - faceted by this volume. And the pacing could be different. Maybe it's faster - paced as the story is approaching a climax or a major turning point.
It might have a more complex plot. As the story progresses, the plot often becomes more intricate, and volume 22 could be no exception. It may build on the events of the previous volumes and take the story in new and unexpected directions.
Volume 13 may differ from previous volumes in terms of the pacing. It could be faster - paced as the story is likely building towards a climax. There might be more action sequences or more intense emotional moments. Also, the relationships between characters could be more nuanced compared to the earlier, more introductory volumes. It could also expand on the magic system or the lore of the world in ways that the previous volumes haven't fully explored yet.
Volume 7 brings some new twists and developments. The plot thickens and the characters face even greater challenges.
It could have some new plot twists and character developments. Maybe the story gets more intense or takes a different direction.