an effective summary should be like a joke set up so the reader will click to get the punch line

Oooh that is a good way of saying it. I like these kinds of summaries a lot! I did once come across a story that was sort of the opposite. The title was actually a "punchline" but you didn't know it until you reached the end. It was rly cool (even tho that isn't rly relevant to summaries or drawing your readers in in the first place dfghj)