Dead of Summer by AJ Merlin

Camp Friends Are Forever Friends
Or so the motto of Camp Crestview says.

Having been a camp counselor for the last three summers, I can handle most situations that come my way courtesy of rowdy children. This year shouldn’t be any different, even with a new counselor who’s everyone’s type and too good to be true. But even so, Kayde Lane is nothing I can’t deal with.
Until I stumble upon him at night with an ax and sinister intentions towards the campers we’re meant to protect
Unable to let him kill anyone, I strike a dangerous bargain with Kayde, only to realize the true extent of his darkness. With every demand he makes, pushing me to the brink of my moral boundaries, I’m torn between survival and the haunting allure of his control.
As the nights pass and Kayde’s demands escalate, I find myself teetering on the edge of sanity, questioning my own desires and the twisted games he plays with my mind.
Seven nights are all I need to survive with Kayde, and if I can do that, everyone lives.
If I can believe the words of a serial killer obsessed with breaking me, that is.