What is this?
I know about teen novels with alternate worlds. Usually those worlds are carefully mapped out, explained, lovingly explored by the author. And I know what is a book with a teenage protagonist who endures a terrible, traumatic experience. Although usually those are girls. It can be rough these days to be a girl in a YA non-fantasy novel. You might get buried alive, or raped, or raped a lot, or accidentally kill your parents, or be in a coma or die, and you will almost certainly be kidnapped. I even know horror. I have read a lot of horror, especially when I was a very young person, and very unsure about things.
So I think The Marbury Lens is horror. But it is non-cheap, un-easy horror.