I’ll definitely check it out! Book Annihilation is very different than movie Annihilation although until I read Chaga I can’t really give an opinion on whether it’s ripping off anything from it. I did a fair bit of research about the book for a university essay and didn’t find any secondary sources comparing the two that I can remember.
Have you listened to Alice isn’t Dead? It’s in a sort of grey area where it could be interpreted as sci fi or supernatural horror. It’s by the creators of welcome to nightmare but way more suspenseful and creepy with less of the light hearted comedy elements.