I’m going to go out on a limb here and say Foundation.

I love the books, they’re legendary, but the show on its own, completely separate from the books, is a great watch. The books are almost like reading a very long thought experiment, it’s more philosophy than story. There’s also a lot of “it was a different time” cringe in the books that does not age well.

Battlefield Earth.

Terrible, terrible, terrible movie…

…but it was shorter than the book - so there’s that.