I'm giving it a generous round up to 3 stars from my believed 2.5. This is why:

Psychologically it is a bit crap. Very stereotypical and not really true to life. However, I found the format a compelling way to tell a narrative about the journey of Dr Harper (because, I belive, that's what this really is.)

I also liked that it did keep me reading. Some parts were too extreme to believe at all but there were the odd moments where I felt like I needed to push on. And I did, onto book two, after this one finished.

I also thought it was good for a short story/novella. I read it in about an hour and a half and wasn't really offended, didn't feel that it ended without a proper character arc and wanted to pick the next one up right away (partly out of a curiosity of how more bizzar can these go but also to find out about the next chapter in Dr Harper's life.)

Is it an amazing example of a psychological thriller/horror? No. Is it wonderfully written? No. Is it an enjoyable, quick, read? In my opinion, yeah. I got it as a kindle unlimited book (during a free trial of Kindle Unlimited) and I've read worse Kindle Unlimited titles.