Mimus by Lilli Thal (translated from German)
The Plot: Prince Florin's father, King Philip, is negotiating a truce between his country, Moltovia, and Vinland. Prince Florin is overjoyed when his father sends for him to join in the celebrations of peace. When Prince Florin arrives at King Theodo's court, he discovers it's a trap; his father has been taken prisoner, his knights and nobles either killed or imprisoned, and now Florin is a prisoner, also. King Theodo finds it amusing to humiliate young Florin by turning him into the lowest of the low -- a jester. Every day, Florin must learn how to keep the king amused, as Florin's father rots in the dungeon and Florin's homeland is attacked.
The Good: This is set in an alternative Middle Ages; it's subtle, done mainly so that Thal can have this be historically accurate yet create her own kingdoms, kings, history and motivation. It works extremely well. The names are slightly familiar: Vinland, Frankenland, Angelland; the history is similar, with references to Persia and the Greek gods. While this isn't "historical" in that it's not tied into real people, countries, or events, it is historical in terms of capturing the feeling of a time and the way people lived.
Florin is totally humiliated by his reversal in life: "sooner or later he would go mad with shame." And isn't that what most kids are afraid of? Shame. Dreams of being in school naked, fears of people laughing. This is combined with a reality of many children's lives: a lack of power: Florin is a captive child, and should he misbehave or try to escape, the prisoners in the dungeon will pay the price in the torture chamber. He has no options. He is powerless.
Florin is given to a fool, a jester called Mimus. Mimus is initially rough with the boy; well, actually, he is always rough with the boy. He's not a nice, compassionate mentor. But he does become a mentor to young Florin. Florin, while not spoiled or arrogant, was privileged; and truth be told, it doesn't hurt him to see, literally, how the other half lives. How the lives of the rich and noble are possible because of those who sleep in straw and eat table scraps.
As Florin adjusts to his new life, he learns many things. Including the origins of the war between his father and Theodo; and what he learns surprises him and shifts his reality. It's not a world of black and white, but of gray. Revenge is sweet...but what happens when it is carried too far? It turns out that Theodo has suffered because of King Philip's actions; isn't he entitled to some revenge? But now Florin is suffering. When does the cycle end? Is it possible to have revenge and forgiveness?
The most important thing Mimus teaches Florin is not how to juggle or tell jokes; it's how to watch. To plot. To plan. To observe. To use what you have to not be as powerless as people may think. Florin the fool may be able to save his kingdom and his father in a way that Prince Florin never could.
This book has action, adventure, and a surprising amount of humor. (Surprising because Florin is constantly in danger and his father and nobles are being tortured). With the right booktalk -- that captures the adventure, the laughs, the danger -- this will fly off the shelves.