I keep hearing recommendations for the Culture books so I tried reading it recently and it just didn't work for me -- I gave up on it halfway through, which is rare for me.
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.