Terry Pratchett and Stephen Baxter collaborating on Pratchett’s The Long Earth

Terry Pratchett and Stephen Baxter are collaborating to finally publish Pratchett’s The Long Earth. Colin Smythe and agent Ralph Vicinanza negotiated the deal, which will see Transworld’s Doubleday publishing the first Long Earth novel in Spring 2012.
The publisher writes “Pratchett first developed his vision of a chain of parallel worlds, The Long Earth, in an unfinished novel and two short stories in 1986, after writing Equal Rites, the third novel in what would turn into the hugely successful Discworld series. Now, at last, this long-gestating concept is to see the light of day in two as-yet-untitled books written in collaboration with Stephen Baxter.”
Pratchett’s description: “Our Earth is but one of a chain of parallel worlds, lying side by side in a higher space of possibilities, each differing from its neighbours by a little (or a lot): an infinite landscape of infinite possibilities. And you can just step from one world to the next…”
Transworld also notes that Pratchett has recently completed I Shall Wear Midnight, the fourth in the Tiffany Aching books, which will be published in September.