I saw the 1973 film The Legend of Hell House before I read Richard Matheson’s book. I liked it. It was spooky fun, a good haunted house film. But some of the finer plot points just didn’t make sense to me. It took the book (“took the book”, that rhymes!) to fill in the gaps. When a medium doesn’t do the job of making me understand the story, it obviously must take second place to the medium that does. And so, the book is better.
I enjoyed the film better after reading the book (watched it a second time), but that is only a testament to the novel’s superiority.
For a more in-depth comparison, read my review of the two (“review of the two”, rhymes again!) Hell House/Legend of Hell House