The titular Avery is a four-year old boy, the son of a happily married couple. He gets possessed, and things escalate quickly.
This was a rather sad and very dark occult-slash-demon possession story - despite the light tone adopted throughout. The character building is incredible, I must say. You get to know everyone better, before the whole mess with Avery takes a sinister, and totally creepy turn. The situation the father faces at work (he's working the night shift at a convenience store) felt completely familiar, and absolutely relatable. His friendship with the deputy, his feelings for his wife, their relationship as husband and wife - all the little details felt just right and hit the right notes again and again.
However, the author shocked me when he chose the ending he did. I'll chalk it up to perhaps being lulled into a false sense of security, and thus caught wholly unprepared for it myself. I think it's meant to be divisive and thought-provoking, but for a story of this length (it's a novelette), it was brutal.