Well written flash fiction is short and sweet but never filling.
Most theorists of the flash fiction story would probably agreed that the idea of writing and reading a flash fiction story is to get to the point. The writer can’t dilly dally and the reader wants a quick payoff. It is the writer’s responsibility not to disappoint the reader. It is the reader’s responsibility to pay attention. Nothing ruins a well written piece of flash fiction faster than a casual reading. This is the unspoken bargain between writer and reader: I will write with focused attention to details and you must read with an unbroken attention to details. For in the details are the implications. Without details a flash fiction story would be a few hundred words on a computer screen that may or may not add up to more than its parts. Good flash fiction is always more than its parts. The parts imply a whole greater than those few hundred words.
Certainly, a reader expects entertainmet. The reader expects closely drawn characterizations. The reader expects believable dialogue and description. The reader expects some sort of conflict or tension and the resolution of that tension. These expectations are the writer’s challenge.
It is my contention that when the human mind becomes aware of conflict or tension there is a natural interest in seeing that conflict or tension resolved in some sort of way. Once the conflict or tension is resolved the reason for reading any further has disappeared. The world and the characters of the flash fiction story don’t disappear, just the conflict or the tension.
And here we have one of the great satisfactions of flash fiction: the reader may want to stay in that world but the story is over. The affect of the story wouldn’t be the same. The flash fiction story only gets one chance to make a good impression.
But if the writer is skillful enough and committed enough and if the writer has enough luck, one reading of the story will satisfy before wearing out its welcome.