For me, “The Running Man” by Stephen King would fit into this. I love the book for the dark, dystopian vision it presents, and its prescient portrait of reality television run amuck. I would love to one day see a serious movie made from it.
But I also love the Schwarzenegger flick, which has almost nothing to do with the book, other than the protagonist having the same name and him competing on a murderous game show in the future. In my mind I see it pretty much as its own thing, which is a goofy, over-the-top, Reagan-era action flick. Not great cinema by any means, but a good “turn-your-brain-off-for-90-minutes, blow-shit-up-real-good” romp, complete with professional wrestler-style villains.
So, what are your instances of liking both the book and the movie, but for different reasons?