He didn't write it, he directed it and is very good directing horror films actually. Maybe his first films weren't Acadamy Awards movies, but that's the way many unknown directors have to start working on, not everyone can start from the top because they know "someone" or are friends "of someone"... I admire this director because he started from the botton and has done a lot with very poor scripts. The fact that now he is doing bigger movies says it all, he has won the right to do so.
This book has a lot of potential, the author is Stephen King's son and he is as good as his father, so I can not wait to see what such a talented director will do now that he has a good story to work with.