The Book of Dust
The in-the-works companion to the trilogy, The Book of Dust will not continue the story, but was originally said to offer several short stories with the same characters, world, etc. Later, however, it was said it would be about Lyra when she is older, about 2 years after Lyra's Oxford, and she will go on a new adventure and learn to read the alethiometer again. The book will touch on research into Dust as well as on the portrayal of religion in His Dark Materials. Pullman has not yet finished writing this work.
Pullman has also told of his hope to publish a small green book about Will:
Lyra's Oxford was a dark red book. Once Upon a Time in the North will be a dark blue book. There still remains a green book. And that will be Will's book. Eventually… —Philip Pullman
Pullman confirmed this in an interview with two fans in August 2007.