Cultural, for sure. I had to tough it out for the first bit, only really liking the detective. But then when all the main characters got replaced over and over, I began to see humanity as the main character, collectively, and then I was hooked, which I’m sure was the intent as the story spans >!all of time in the universe 2 times over,!< It’s worth revisiting.
I would suddenly feel very sad for the one of them that bottled it up for 40 years, and for the other who obviously has known for many of those years…