Filler and more filler. As the author says at the end: 'Volume 15 is going to be the preparation for the final battle, and Volume 16 will be the last volume, but I feel like Volume 15 won’t be exciting enough in that case.'. And it sure isn't! She could have taken half the next book, throw away the filler and graft said half into this book.
Anyway, just avoid these chapters:

S1 Waking to a New World
S2 The Value of a Life
S3 There’s No Point Dwelling on Past Misfortunes
Interlude Kunihiko Tagawa
Interlude Kengo Natsume
Interlude Yuri

The rest of the book is sort of 'OK', but the necessary info for understanding what will happen in the next book is mingled with the filler, so you can't skip it as easily as the first chapters.