A Book of a Thousand Days by Shannon Hale

. A plucky and resourceful orphan, Dashti comes from a nomad tribe in a place resembling the Asian Steppes, and is brought to the Lady's house in the midst of a crisis. Lady Saren, having refused to marry the powerful but loathsome Lord her father has chosen, faces seven years' imprisonment in an unlit tower. Initially, Dashti believes her worth is tied to her ability to care for her "tower-addled" lady until she can join Khan Tegus, to whom she is secretly betrothed. When the gentle Tegus comes to the tower, Dashti must step in for her traumatized lady, speaking to him as Saren through the one tiny metal door. Hale exploits the diary form to convey Dashti's perspective; despite her self-effacing declaration that "?I draw this from memory so it won't be right," the entries reflect her genuinely spirited inner life. The tension between her unstinting loyalty and patience and burgeoning realization of her own strength and feelings for Tegus feels especially authentic. Readers will be riveted as Dashti and Saren escape and flee to the Khan's realm where, through a series of deceptions, contrivances and a riotously triumphant climax, the tale spins out to a thoroughly satisfying ending.