Well-written characters. It can have the most boring plot in the world, but if the characters (and interactions between characters) are well-writen, I'm down.

Oh, he's the original writer one of my favorite anime of all time (Another)! I'll def check it out, thank you for the recommendation!

I haven't! It looks interesting, will definitely check it out. Thanks for the recommendation!

Remote island (or any isolated places) murder mysteries.

Agatha Christie's And Then There Were None is my #1 most reread book, haha.