- "Maybe one day. Lyra et les Oiseaux (French equivalent for 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's response in a 2007 interview with fans when asked about more information on Will.
The Green Book is a possible future companion book to the His Dark Materials trilogy. It will focus on Will Parry, as the dark red book focused on Lyra and the dark blue book focused on Lee Scoresby. First mentioning the book in 2007, Pullman has since confirmed his intentions, stating that he wishes to write it after the completion of The Book of Dust.