This is the third book of a fantasy trilogy. It takes place sometime around 1500 when folks really believed in magic. Reminds me of Lloyd Alexander's BEGGAR QUEEN and of Funke's THIEF LORD.
The story revolves around many people's need to possess an ancient book which is believed to contain the secrets to immortality. Boy and Willow are street kids who work for Valerian for just enough food and warmth to survive. Valerian is a famous actor who dabbles in magic, astronomy and possesses the book in question. The king's men kill Valerian, ransack his home looking for the book. Willow and Boy on the street again are rescued by a sort of friend of Valerian. Kepler wants the book and Boy. He sends Willow to a work house from which she escapes. Boy returns to Valerian's house to get the book for Kepler. He is captured by the King's men lead by Maxim. The king has no heir. The king wants to live forever so his reign will not end. People who claim to know how to make him immortal but are proven to be fake are sent to a phantom monster in a lower dungeon of a castle. The same fate waits Boy for not revealing what he knows about the book. For reasons we don't know until the end of the story, Kepler who now has the book is determined to rescue Boy from his castle prison with Willow's help they arrive as entertainers. Thought they are not allowed to leave, they are not exactly imprisoned either. An innocent question by boy leads Maxim to a solution to the immortality problem. Boy, who the king has become fond of announces to the audience the fraud Maxim has just performed pretending to make the king immortal. Chaos ensues and eventually every thing is sorted out but not before many deaths on the part of the phantom who's identity is revealed as well. JDW 9/19/07