The Red Pyramid (The Kane Chronicles, Book 1)

Since their mother's death, Carter and Sadie have become near strangers. Sadie lived with her grandparents in London while her brother traveled the world with their father, Egyptologist Dr. Julius Kane. One night, Dr. Kane brings the siblings together for a "research experiment" at the British Museum, where he hopes to set things right with his family. Instead, he unleashes the Egyptian god Set, who banishes him to oblivion and forces the children to flee for their lives.