ONE OF NPR'S BEST BOOKS OF 2019 Two time-traveling agents from warring futures, working their way through the past, begin to exchange letters--and fall in love in this thrilling and romantic book from award-winning authors Amal El-Mohtar and Max Gladstone. In the ashes of a dying world, Red finds a letter marked "Burn before reading. Signed, Blue." So begins an unlikely correspondence between two rival agents in a war that stretches through the vast reaches of time and space. Red belongs to the Agency, a post-singularity technotopia. Blue belongs to Garden, a single vast consciousness embedded in all organic matter. Their pasts are bloody and their futures mutually exclusive. They have nothing in common--save that they're the best, and they're alone. Now what began as a battlefield boast grows into a dangerous game, one both Red and Blue are determined to win. Because winning's what you do in war. Isn't it? A tour de force collaboration from two powerhouse writers that spans the whole of time and space.