Why do books make terrible movies?

I wonder why it’s so hard to make a movie from a book, or, why do so many book to film adaptations suck?

James Patterson is a fantastic writer, Alex Cross is one of my favourite detective / thriller series, but boy was that Alex Cross movie terrible.

Zoo, another James Patterson book, was a terrible TV show. It barely ressembled the book.

Another author I quite like is Stephen King. His book to movie adaptations are pretty ordinary too, sure there were a couple of good ones, IT, The Shining, The Stand, Misery, but for the most part they weren’t remotely as good as the book.

Why is it so hard to make a good movie from a book? Is it the acting choices, is it that books can be way more descriptive, what is the missing ingredient?