I will preface this by saying that the following contains a spoiler for Michael Chabon's The Yiddish Policeman's Union, so tread carefully.
Chess features heavily in the book and a major plot point is a seemingly in-progress game that a young man was playing while he was murdered. However, at the end, it turns out that it wasn't a game at all - it was a puzzle. Here are the details of the puzzle as it is described in the book.
- White still has two knights on the board in the position.
- White to move and mate in 2. (Not 3, see comments under answer below)
- White can try by underpromoting the b-pawn to a third knight. (Tempting, but not the key, see comments under answer below)
- Black has a pawn on d7 that he must move at this point, though it is unclear if it is because this is the only legal move, or if failing to do so would lead to a quicker checkmate.
- White instead plays the move Bc2, a move described in the book as, "a dull move [that y]ou don't even notice it at first."
- After White plays Bc2, Black is in zugzwang, and is compelled to move into their own eventual loss.
- Had White not played 2.Bc2, then White would still have mate in 3, not mate in 2.
Is this a real, pre-existing puzzle that anyone is familiar with? It sounds an interesting, but I can't work the mechanics of it out in my head. Surely the Black king must be in a wildly precarious position for the move 1.b8=N to be necessary - the only way I can rationalize it is if it somehow leads to a mating net, necessitating the king to be in the general vicinity of, say, a5. I'd love to know if something real can be made out of this, or if it's possible at all.