What is the title of the first children's book co-authored by Stephen Hawking and his daughter?

The first children’s book co-authored by Stephen Hawking and his daughter Lucy was George’s Secret Key to the Universe. Published in 2007, it was written with Christophe Galfard and introduced young readers to astronomy, astrophysics, and cosmology through an adventure story.

The book follows George Greenby, a boy who discovers a powerful computer named Cosmos. Through the story, readers encounter planets, stars, atoms, black holes, and other ideas about the universe. Informational fact files and illustrations accompany the fictional narrative, helping explain the science behind the adventure.

The title is often confused with later books in the same series. George’s Cosmic Treasure Hunt came next in 2009, followed by George and the Big Bang in 2011 and George and the Unbreakable Code in 2014. Those are sequels, not the first book.

Stephen and Lucy Hawking created the series to make difficult scientific concepts more approachable for children. The collaboration also helped extend Hawking’s public role as a communicator beyond adult popular science books.