I learned a lot growing up from his books.
Especially how to not take the surface or "given" explanation for everything.
One of my favorite Vonnegutt writings (which I can't seem to locate anywhere online) was the text of a speech he gave to an association of psychiatric professionals.
It was a self-congratulatory convention, and they had paid for a vonnegutt speech to honor themselves.
Vonnegut delivered a speech that featured a fictional account of a young nazi concentration camp guard being "cured" by his shrink of depression and angst. It featured the punchline, "If you hadn't come to me when you did, your doubts and fears would have continued to grow, and eventually, you may have even entertained thoughts of killing Hitler!"(I am paraphrasing)
It was a typical vonnegutt move, leading them down the garden path, only to point out with a short and funny story that the whole concept of psychiatry is pretty much a sham.
Whenever I see one of his books lying somewhere, I can pick it up, begin reading at any point inside, and lose all track of time..Very few, if any, other authors I can say that about.