I love that feeling when you've been so into a book that you don't realise that it's really late and everyone around you has fallen asleep, then you read this really funny sentence or phrase and you're like ...oh no... because next thing you know you're rolling around on your bed while trying to keep the laughter in so you don't wake anyone around you up. 
So in the end your just laying there looking like a total maniac with tears of joy streaming down your face while convulsing with silent hysterical laughter...
You know what I mean?