Terry & Stephen team up for The Long Earth

Two authors that I really enjoy (Sir Terry Pratchett & Stephen Baxter) have teamed up in a joint effort in The Long Earth. I can't tell you how good this book is yet, as it has literally only just landed on my reading shelf. Usually I am somewhat nervous about joint author efforts, as sometimes it goes horridly wrong, but I'm pretty sure I am going to enjoy it no matter what.

I'll tempt you with the synopsis from Publisher's Weekly :

In this thought-provoking collaboration, Pratchett (the Discworld series) and Baxter (Stone Spring) create an infinity of worlds to explore. A revolutionary process known as Stepping has allowed humanity access to an unlimited number of parallel Earths, all devoid of human life. The further one travels, the stranger the variant worlds become.

Joshua Valiente, one of a rare breed who can Step without external help, is hired by the transEarth Institute to travel by airship across the Long Earth, exploring as far as possible. Accompanied by Lobsang, a Tibetan reincarnated as an artificial intelligence, he journeys across millions of Earths, discovering just what sort of bizarre secrets lurk in the farthest reaches.

Has anyone out there read it yet? Willing to share your thoughts on this collaboration?