Comment by Cthulhu_

And yet, it's not unusual that a poorly written book gets a decent movie adaptation. Sometimes it's not even a good plot OR well written, sometimes a book is just popular and the execs cash in on its popularity.

I'm thinking things like Da Vinci Code, 50 shades, Twilight, neither of which (the books) are particularly good or tasteful or whatever, but they were very popular, appealing to people who normally don't read books.