PSA: The "Culture" novels by Iain M Banks are fantastic and can be read in any order. "Player of Games" was the 1st one I read and still probably my favorite.
The first book Consider Phlebas isn't bad, but it isn't as well developed as the rest of the series IMO.
My reaction is perhaps summarized by the old quip: "This is not a novel to be lightly tossed aside. It should be thrown with great force.".
It wasn't any one thing but I eventually hit a point where continuing just wasn't worth it for me. There's too much else on my to-read shelf which is less likely to seriously annoy me.
Stephen R. Donaldson: He's more known for The Chronicles of Thomas Covenant, but you might prefer The Gap Cycle; it's more typical SF.
Also, the Night's Dawn trilogy by Peter F. Hamilton. Perhaps Dan Simmons? And of course anything by Charlie Stross.