The Book of Dust is an upcoming novel by Philip Pullman

Philip Pullman

Philip Pullman CBE, FRSL is an English writer from Norwich. He is the best-selling author of several books, most notably his trilogy of fantasy novels, His Dark Materials, and his fictionalised biography of Jesus, The Good Man Jesus and the Scoundrel Christ...

. It will be a companion novel to the His Dark Materials

His Dark Materials

His Dark Materials is a trilogy of fantasy novels by Philip Pullman comprising Northern Lights , The Subtle Knife , and The Amber Spyglass...

 trilogy, and will feature Lyra Belacqua

Lyra Belacqua

Lyra Belacqua , also known as Lyra Silvertongue, is the heroine of Philip Pullman's His Dark Materials trilogy. Lyra is a young girl who inhabits a universe parallel to our own...

 as a main character. The story will take place two years after the events of Lyra's Oxford

Lyra's Oxford

Lyra's Oxford is a short book by Philip Pullman depicting an episode involving the heroine of His Dark Materials, Pullman's best-selling trilogy. Lyra's Oxford is set when Lyra Silvertongue is 15, two years after the end of the trilogy...

and will tie into that book. Pullman has said that Lyra will be "about sixteen." The book will also be "about Dust

Dust (His Dark Materials)

Dust in Philip Pullman's trilogy of novels His Dark Materials is a mysterious cosmic particle that is integral to the plot. In Northern Lights, Lord Asriel reveals the origins of the term "Dust" to be from a passage from the slightly alternate version of the Bible in Lyra's World: "In the sweat of...

," and will address the lack of positive portrayals of religion in the His Dark Materials books, although it will not be a continuation of the trilogy.
Pullman conceived of The Book of Dust before the publication of Lyra's Oxford in 2003, but had not begun writing it at that time.