I feel like I have read quite a few books that I felt that way about, but it's always hard to bring them to mind when someone asks. That said, the first few that popped into my head:
The Bobiverse (series)
4th book was such a disappointment.
Overall message too, somehow went from "we are the avantgarde of transhumanism and the universe is our playground" straight up to something like "i wish 50's back". Every single Bob turned to either flat meme or boomer.
Gibson's sprawl trilogy when I read them back in '89. The fact that it had many short chapters made it easy to consume in quick bursts of reading
I love all of Gibson's books, have you read anything by Pat Cadigan? Fools may be the most mind bending book I've ever read, in a good way
A few books that kept me captivated recently
The Mote in God's Eye
Book reader community.