The Long Earth - Everything2.com
The Long Earth The Long Earth Missile Gap. A strange new megalithic world appears from nowhere, and everybody runs around exploring it. This is a well-trodden and quite entertaining trope in science fiction, but it is worth noting that it is not really Terry Pratchett's thing, and these books show very little of his humor and character development. I haven't read much of Stephan Baxter's works, but I would assume that this is novel was much more influenced by him. One day an unknown inventor posts instructions on how to build an odd device on the internet. For reasons never clearly explained...
Source: everything2.com