When films are adapted from books, more often than not, I tend to find the books a lot more enjoyable. So I have skipped watching a lot of films in the hope of reading the books later.
So what are some great films not adapted from books? Or what are some films that are significantly better than the book they were adapted from?
Yea, in the case of Star Wars, there's a lot of borrowing from old ideas and mythological forms as well as the samurai and western genres that I'm not sure it entirely counts ... it probably sits in its own little category of sort of fairy tale literature brought to film, which is an achievement in its own right.
It's not just about borrowing from older ideas, it's about the extent to which star wars was knowingly channeling a certain kind of story structure that has old cultural roots.
The Lion King would be a similar-ish example. It's basically Hamlet, which Shakespeare based on an older Viking story (AFAIU) ... so it's just one of those stories that's out there.
None of which is to criticise Star Wars, just to argue that it stands separate somewhat.
I'm vaguely aware of those influences, but decided to answer OP's question very literally (there's no 'New Hope' book that anyone can check out after seeing the first film)