I have no idea what to say about this one. I think had I read it it may have been 5 ⭐️ but listening to it I found parts confusing. I wasn't sure if the voices were in her head or they were people speaking to her at times. That being said I also feel like that was part of it, to be confused. It's written in a first person narrative so my confusion felt like Mary's confusion also.
I enjoyed it, I was expecting gruesome and scary, I definitely got gruesome. This one isn't going to be for everyone and although the narrator did a great job I recommend reading it over listening. 
Don't skip the authors note at the beginning and the afterward, read by the author on the audio. I enjoyed hearing about his personal experiences.