It's because every character was made to be an archetype and Hendrix didn't do anything to elevate them above that. Even worse, instead of just using cookie cutters to build his own arcs, he just recycled the experiences of the "final girls" upon whom his cast was based. It made them feel overly familiar, and once you realize that they'll never be anything but, it's easy to check out.

I'll be honest, I think Final Girl Support Group is by far the weakest thing he's ever written. It's sloppy, fully of typos, poorly edited, and crazily unstructured - throwing out its concept like a third of the way in, ditching the entire ensemble along with the support group itself to focus instead on the unlikable lead and somebody introduced far too late for the reader to care about. I also found the climax and everything leading up to it surprisingly underwhelming, with a bulk of the slasher action occurring off page. It's not a terrible book by any means, but it also didn't read like that of a professional for me. And that's coming from someone who absolutely adored My Best Friend's Exorcism and Horrorstor.

Funny enough, Hendrix himself admitted he tried to sell the novel in 2014 and was refused at every turn. He blamed it on Riley Sager, who's book he claims he never read. But if I had to guess, it's much more likely it didn't sell because of its quality, and that it was published when it was thanks to Hendrix' success with his other, successful novels.