What carries the book is the tone; sarcastic but warm, as though the funny guy had suddenly decided he wanted to be friends with you. Culture, language, stupidity, and the protagonist are all the butt of jokes at various points.
In its final pages, Don’t point that thing at me takes a twist into a very different direction; a serious tone imparting a serious message, based on the consequences Charlie suffers as a result of his choices. That felt odd to me. It was only when I realised that there was a trilogy (and therefore the consequences for Charlie can’t have been as consequential as they appeared) that I realised that even that, final, shift in tone was likely a joke too.