OK, I have an extremely controversial one:
The Stand by Stephen King
I know, I know. It wasn’t the original but his expanded version. And I found it so unbelievably ponderous with King belaboring every point. After about 200-250 pages, and realizing I was nowhere close to getting into the actual heart of the story, I gave up.
The only sequels we all ever wanted were the Thrawn Trilogy.