Absent by Katie Williams

Has anyone read Absent by Katie Williams? Watching School Spirits I immediately thought it was a loose adaptation of that book. It's about a girl who dies at school and her ghost is trapped there. If she tries to leave school grounds she ends up back where she died. One of the other ghosts is a gay student whose in-life crush is now a current teacher. A lot is different (no murder plot) but even the twist of school spirits (possession) is a major plot of the book. Which had me guessing that option right in the beginning of the show! I am just thinking someone else must of read that book, seen the show, and noticed the similarities!