The Long Earth is a concept Terry Pratchett first developed back in the mid-80s, around the same time that he was finishing up the third Discworld book, Equal Rights. The novel was a victim of Pratchett's own success, getting left behind when the Discworld series proved to be so successful. Sadly, as much as I wanted to like it, and as promising as the first few chapters were, it really does feel like a book that was written 25 years ago, handed off to somebody else, and then rushed into print. Nothing against Stephen Baxter, who is an amazing author on his own, but this is an awkward collaboration that really adds nothing to my Pratchett shelves.
The concept here is definitely intriguing, even if it's not quite fully explained. Basically, humanity has discovered the ability to 'step' between parallel worlds. There are those among us who have always been able to do so naturally, without really understanding what they've done or how, but one man's eccentric experiments have bestowed that ability upon anybody willing to construct one of his little 'stepping' boxes. Suddenly, humanity has access to an infinite number of pristine worlds, as ripe for exploitation as they are for exploration.
There are some interesting catches, of course - stepping makes most people violently ill, nothing made of iron can move between worlds, and stepping from atop a skyscraper to a world without buildings is a really bad idea - but the possibilities are endless. What makes the first half of the book so interesting is the unexpected consequences of stepping. Criminals suddenly have easy access to even the most impenetrable places on Earth, forcing governments and banks literally underground. Greedy explorers invest everything they own to replicate the gold rush on other worlds, only to find that everybody else had the same idea, and that gold has been rendered worthless. Immigration is pretty much a thing of the past (why apply for visas and passports when you can just 'step' somewhere new), and governments are left scrambling to keep the infrastructure and economy running smoothly with half the population suddenly gone.
Those side-tales, however, are also part of what's wrong with the book later on. Pratchett and Baxter spend far too much time relating stories of the new explorers when, in the grand scheme of things, they really add very little to the story. Similarly, as interesting as it is to reexamine some urban legends by imagining the participants were natural steppers, they go back to the well far too often, and the stories that were so entertaining early on just become annoyances later. Unfortunately, it turns out these asides are necessary to keep things moving, since the central storyline just isn't strong enough or interesting enough to carry a whole novel.
As for that storyline, we have a natural stepper who has become something of a reluctant celebrity because of his heroic actions the night the rest of the world learned to step. We also have a sentient computer who believes himself to be the reincarnation of a dead human, and a shadowy organization who employs them both. The two set out on a mission to explore their way to the heart of the Long Earth (assuming there is such a thing), stepping across hundreds of thousands of worlds on their journey. If you've ever watched a child flick through the channels on TV, stop every once in a while to watch a few minutes of a show, and then keep flicking again, you've basically shared the experience of the book. They do have some adventures, and do discover some interesting facts about how we're not alone in these parallel worlds, but there's far too much filler between the facts.
In the end, this felt very much like a young-adult novel that wants to be more, the kickoff to a series that really seems to have no clear direction ahead. It comes across as somewhat lazy and haphazard, with flashes of brilliance, but an overall dullness that left me skimming chapters by the end. Not even a surprising act of anti-stepper terrorism at the end can rescue the overall story.
While I didn't expect a Discworld level farce, Pratchett's trademark absurd humour is largely missing here, aside from a few quirky (but unusually subtle) bits. It's a shame, because that might have helped to carry the story. The Discworld novels are not exactly the most amazingly plotted works of epic fantasy ever to grace the shelves, but they are fun reads that understand how to continuously engage the reader. That engagement, more than anything else, is what is missing here, leaving us with a story that doesn't live up to the concept, and characters who are too one-dimensional to carry one Earth, much less hundreds of thousands.