That's a valid point, so I'll just clarify what I mean.

>isn’t every move a character makes in a book written solely for the author’s need for them to do so?

Yes and no.

On the most obvious level, it absolutely is.

The problem comes when a character does or says something that they have no reason to do or say other than the author needs them to.

So, in this example, the character says something because the author needs to create tension. That's fine. But what a competent author would do is give the character a reason for saying it.

Actions should be driven from character and/or story, not just a bunch of random stuff happening because it is convenient for the author. Because not only is this bad writing, but it is contemptuous to the readers.

This is the main problem I have with this book (aside from having the stupidest plot twist in all known literature). The whole world and everyone in it only act the way they do because the author needs it. Their actions aren't derived from character and the way things work (such as everything in the mental hospital) are set up to be convenient to the author.

Sure, people are free to take liberties, but if you're going to write about something, there needs to be at least some level of plausibility, which this completely lacks.

Honestly, I was so excited for this book and am a big fan of the pulpy, twisting mystery thriller, which is probably why this was such a massive let down. It wasn't even the hype (I picked it up randomly in a second hand book store), but it was such a poor effort on any other level than needs to be twisty that I couldn't help but be appalled.