Hmmmmm I didn’t finish this book past chapter 6. My advice for the author is to rethink the first person POV and try third person first if they are a new writer (which, I assume they are). First-person POV is much more difficult to write without seeming tacky. Third-person may also help the horror factor and suspense because then the reader will know more than the main character.
Other advice would be to avoid information dumping in the beginning chapters. A great example of an author who gives relevant background information in an interesting way is Laura Hillenbrand, especially in the book Unbroken. Dark Detained’s context felt more like a rushed essay than an interesting background.
Some easily fixed mistakes could be pointed out by having more readers revise this book before it was published. Even just using a free program like grammar.ly may have helped.
My final pointer about the portion I read is that this novel doesn’t seem very engaging or in tune with a younger audience. The opening points about technology were particularly disheartening, and by showing this bias the author is likely to turn modern readers off of his book.
I wish the author the best! No matter what criticism they receive, they wrote a book, and that’s awesome!!!