"The Long Earth" by Terry Pratchett and Stephen Baxter

Like all good sci-fi, The Long Earth begins with a compelling premise. One day, in the near-ish future, a design for a device simple enough for kids to put together appears on the internet. Soon, thousands of people have built the device and immediately "step" into a parallel Earth. In the time that follows, people discover an infinite number of parallel Earths going in two directions from what is now called "Datum Earth." There are oddities of course--most people experience severe nausea from stepping, and though the stepper takes whatever he or she is touching along for the step, no iron can be passed between worlds. Each of the parallel worlds retains the same underlying geography--if you step from New York, you step into the New York of the parallel word--but none of the parallel worlds have people or modern development. Instead, each world appears to represent a "potential" world that our physical world could have evolved into a some point in its history.

What I liked most about this premise was that it allows for a lot of exploration into how such technology would affect our current world. Early on, many people begin to settle the parallel Earths, but it's mostly the middle class--the rich have too much to lose in leaving Datum Earth, and the poor have insufficient resources to make such a trip feasible. It's also noted early on that a small portion of the population is unable to step, creating hostilities. I thought both of these issues were interesting, but unfortunately they make up a small portion of the novel.

I also thought the psychology of why people would leave Datum Earth was interesting. At first, I thought there's no way I'd leave the modern conveniences--not just cell phones and the Internet but toilets and modern medicine--to start over in a new world. But, the more I read, the more I could see the appeal of leaving behind the burdening details and concerns of the modern world (buying insurance, investing in retirement properly, paying taxes, etc.) and focusing just on subsistence and survival. Such an idea certainly excessively romanticizes "pioneer" living, but I could understand the desire for such a life.

But, again, a lot of those issues are pushed aside to focus instead on the story of Joshua, a bit of a hero stepper who can step naturally and without getting sick, and Lobsang, the first artificial intelligence to be recognized as a person by the courts. Lobsang hires Joshua to travel with him millions of Earths beyond Datum Earth. Unfortunately, their story--traveling through world after world--and their relationship--Joshua getting accustomed to Lobsang's quirks--are pretty dull. Neither person is especially exciting as a character, and I found myself more engaged when the story strayed to other people or places.

I still liked the book and will read the sequel. There's enough interesting worldbuilding and lots of potential exciting storylines to bring me back, even though I hope Pratchett and Baxter find a new way to use Joshua and Lobsang in the future.

A side note: My husband went into The Long Earth expecting the humor and absurdity associated with Pratchett. He kept laughing--trying too hard I think--at things that weren't especially funny, and he had a hard time believing me when I said it's not a funny book. It's not--there's some humor, but it's fairly serious sci-fi. That's not a criticism in and of itself, just something to be aware of.