I saw The Young Poisoner's Handbook at the cinema during the original run, but haven't seen it since. I remember liking it, and like you enjoyed the darkly comedic aspects.

Speaking of which, I completely understand what you are saying about finding something darkly hilarious when others around you don't.

Relatively recent example: Gone Girl. I saw it in a packed cinema, and was laughing out loud at a lot of the satire and the much darker film noir tropes, but no one else in the audience was laughing. I tried to stifle my laughter as I was painfully aware I was the only one amused. Am I just a sick, twisted individual? Apparently not, as I read an interview with Gillian Flynn, and she said when she wrote the screenplay (adapting her own novel) she deliberately upped the black comedy.

So at least I'm in good company.