Vonnegut uses non-linear storytelling to describe severe, war-induced PTSD in a unique and imaginative way.
Being oblivious is dangerous.
Being self-aware will keep you in line with the heard.
There's safety in conformity, whether it's fair or not.
This book feels every bit of its age to me (87 years old). It doesn't give bad advice necessarily, just basic positive thinking encouragement. Some good nuggets of wisdom, but this can easily be absorbed by reading a detailed summary or viewing a YouTube video outlining the main points.
Steinbeck writes about our need to connect with each other and how we will subject ourselves to great inconveniences or even great pain to pursue this. Many characters lament their loneliness and pursue fellowship with one another, even though people so often tend to complicate life and bring us grief.