This novella is delightfully intriguing and imaginative. It follows two time travelling operatives from opposing sides, Red and Blue. While they’re altering threads of history in multiple universes on behalf of their respective empires, they begin to leave secret messages for each other. As their relationship grows, they eventually fall in love.
Told threw narrative and their letters to each other, it does a wonderful job of seamlessly moving through time and space and finding increasingly inventive and unexpected ways to leave messages.