For me, the most recent book regret is Dark Matter by Blake Crouch. Predictable from the get-go, bland, boilerplate sci-fi ideas, too many of these way-too-convenient plot devices just to push the story forward. I frankly don’t get the hype, and I am a pretty big science fiction guy.
Another one is Blink by Malcolm Gladwell. I read this in college and this whole book should have been a one-page essay. It was too repetitive, and the whole premise of “trust in your snap judgments and gut reactions” is way too simplistic and honestly stupid. Like all Gladwell books, it was anecdotal, superficial, and a waste of time.
Even my most disliked books provoked thoughts and feelings when I read them. I still think about them from time to time which means they stirred something even if I didn’t enjoy the read.
Something I tell myself occasionally is that every book I read can’t be 5 stars, and if it were that would be quite boring. Variety is the spice of life. I very rarely DNF, and I never regret having read a book.
This is very much my take on it too. I’ve never been big on DNFing books and as much as I’ve hated some books, I’ve never actually regretted reading any of them. Every book provokes thoughts and feelings, as you say, and imo those are worth having even if about something I didn’t like. I’ve always found something to reflect on, in some shape or form, in every book.