The title of this book is kinda misleading, I think. Maybe it was intended to drum up excitement in a way that may not have been needed. The first book of the Long Earth spans across more than a million alternate Earths that we are now able to "step" across, and the implications are explored at least in the early days quite well. 
 This one takes place 25 years into the colonization phase and we're in a cooperative space with "trolls" humanoids that grew up being able to "step" and have a singing language that is much smarter as a whole for their species than is generally understood by us stupid humans. 
 Of course, the idiots of our species start killing them off while others work with the others in tandem, and then there's also the OTHER humanoids we jokingly named Elves and Kobolds and First Person Singular (for a singular intelligence that developed to devour whole Earths). 
 This might be the reference to the title, but if so, it's more about humans fighting human nature and trying to limit the danger of our shortsightedness as bigots on Datum Earth (Or original home) spew vitriol about all the people who left, turning into a religious and economic and political quagmire. 
 Even so, this book still remains, at its core, an adventure that's part western, part hard-sf, and all a brilliant mesh of Baxter's vision and science and Pratchett's great worldbuilding and characters. 
 Oh, and the end is a real kicker. I can't wait to get on the rest of these novels. It's damn fun and easy, despite its apparent hard-sf premise of many-worlds. :) MANY worlds. :)