The Empire of darkness - Christian Jacq

Egypt is a shadow of its former self. An army of barbarians, mounted on horse-drawn chariots, has swept through the Empire, destroying everything in its path. Known as the Hyksos, the 'leaders from foreign lands', they have reduced the land of the pharaohs to slavery.
Only one city resists: Thebes, where the widow of the last pharaoh, Teti the Small, still reigns. But Teti knows it's only a matter of time before her men succumb to the barbarities of the cruel Hyksos. She has an 18-year-old daughter, however: Ahotep. Fierce, beautiful and courageous, Ahotep will never accept defeat. And so she decides to re-ignite the flame of Egyptian resistance. All by herself.