At North American Discworld Convention last year the authors were talking about this book, and it didn't sound very interesting to me. But when it came out, I thought what the heck and decided to try it.
The Long Earth is based on the idea that there are infinite Earths, side by side, and in the beginning of the book people learn how to step across from one to another to another. You cross to another Earth, and you're in the same place, geographically, but it's another version of Earth that's slightly different. There aren't humans, for one thing, so what you get is wilderness and all the wildlife that would have lived if humans hadn't killed them. You step again, and get to another, similar but slightly different version of Earth. And so on. This sets off a frontier impulse in a lot of people, with new worlds to explore and settle, and new natural resources to exploit. People set up their own communities and communes a few steps away from our modern Earth, and in the meantime the old Earth is emptying out. Not of everyone -- some people choose to stay or cannot leave. But it causes enormous changes in the main world as well as all the others surrounding it.
The story is told through multiple viewpoint characters as the authors explore all the possibilities and the implications of how this change would affect everything else. In that, it is very traditional science fiction. Though there are many storylines, the main one is about Joshua Valiente, who is unusual in that he finds the stepping process much easier than most people, and prefers to spend most of his time alone in uninhabited Earths. He is persuaded to accompany a powerful AI on a journey to explore farther than anyone else has ever gone.
The problem with this book, and I am currently two-thirds of the way through and unlikely to continue, is that this is a Big Dumb Object story. The whole point of the book (so far) appears to be exploring this amazing and mysterious new thing they've found. (For those unfamiliar with this story type, it's less common than it used to be. Well-known examples are Rendezvous with Rama and Ringworld.) And the thing is, it's boring. I am neither interested in a straight SFnal "let's extrapolate how this will change society" exercise, nor am I interested in pioneer fiction, having been fed more than a lifetime's supply of that in my childhood. And I never enjoy science fiction that tries to show me the scope of a setting or situation by hopping to lots of point of view characters.
So I have lost the will to keep reading this book. I have been avoiding it, and forcing myself to pick it up and read a bit more, but I have a big pile of other things I'll probably like better in the To Be Read pile, so I am not going to further waste my time. It's probably a fine example of old-fashioned "let's extrapolate the consequences of this change" science fiction, but it's not for me.