This Is How You Lose the Time War by Amal El-Mohtar and Max Gladstone (SF Novella, 2019).
This splendid novella brings together the special talents of the award-winning Amal El-Mohtar and Hugo-nominated Max Goldstone.
Two factions, one high tech-centered and the other nature-based, wage a sprawling war for dominance through time itself. Despite their differing word-views, the factions and their agents employ much the same methods to shape and re-shape and re-shape history yet again. From the earliest days of human civilization, clear into the far future, agents kill key people, or keep them from being killed, or otherwise influence the timeline in ways both subtle and gross, amusing and ruthlessly violent.
Red is the foremost operative of the Agency (the technotopia); Blue works for the Garden. They are enemies, yet come to admire one another’s abilities and even their special styles in fighting this bizarre and breathtaking war. Finally, intrigued, one secretly contacts the other. They begin to compare notes with creatively hidden messages that would get either (or both) executed as traitors (conspiring with the enemy, etc).
Even as they move from era to era, causing trouble for the unknowing and hapless people whose destinies they change with cheerful indifference, they become closer. Without meeting face-to-face, they finally come to love each other. One faction becomes aware of the other’s apparent attempt to make contact and demands their super-spy set a trap for the other. A multi-level battle of wits develops and plays out to a stunning conclusion, as the agents now try to outwit their superiors and find a way to get out of the war together.
This struggle itself may be endless, but the two characters might just find a way to a sort of personal win. To find out how, read this short yet satisfying book.