The Egypt Game by Zilpha Keatley Snyder. A group of unlikely friends get together after school and pretend they're ancient Egyptians. A significant subplot involves a serial killer of children, so sensitive kids might not be able to handle this one.
3. Cleopatra VII: Daughter of the Nile, Egypt, 57 B.C. (Royal Diaries) by Kristina Gregory. The fictional diary of 12-year-old Cleopatra, who lives in the dangerous royal palace of Alexandria. In order to escape the long arm of her ruthless and politically ambitious older sister Tryphaena, the young Cleopatra goes with her father to Rome, where she meets the handsome young soldier Marc Antony and a little boy named Octavian.
2. Pharaoh's Daughter by Julius Lester. The biblical story of Moses (called "Mosis" in the novel) and his fictional older sister Almah. References to cultural nudity and lust.
1. Mara: Daughter of the Nile by Eloise Jarvis McGraw. A classic novel about Mara, a blue-eyed, sarcastic slave girl who finds herself caught up in political intrigues. Read my review.
Honorable Mention: It's a middle-grade novel rather than a YA novel, but Jill Rubalcaba's A Place in the Sun is a great book.