It goes like this: the first 4 chapters, which make up the vast majority of the pages, are a psychological novel set in our world and current year. Each chapter has a different protagonist, and all 4 knew each other at some point. So, rather than 4 completely random and different stories, it's like 4 different outlooks on the same story, with lots of references between them.

The point of those chapters is to explore their psychological struggles, that may vary greatly between characters but all share a certain core: the meaning of life. If I were to describe what they go through in this story is that they learn what it means to be human.

Then there's the 5th chapter, which is a philosophical science fiction. The point made since the beginning of the book is that there was someone observing everything that was going through with those characters, and now this is his chapter. It's a wrap-up that ties all the themes that seemed loose before into something more concrete.

And finally the 6th chapter turns the story into a metafiction just to push those themes even further.