THE LONG EARTH

Pratchett, author of the esteemed Discworld yarns (Snuff, 2011, etc.), and collaborator Baxter (Stone Spring, 2011, etc.) venture into alternate worlds.

Eccentric, reclusive genius Willis Linsay of Madison, Wis., publishes on the web instructions for building a strange device consisting of a handful of common components, some wires, a three-way control and a potato. A flick of the switch ("west" or "east") sends the builder into an alternate Earth—one of a possibly infinite sequence—where there are no humans at all, though there are other creatures descended from hominid stock. Some people are natural "steppers," able to step into the Long Earth without any device. Another minority are phobics, unable to step at all. Steppers can take with them only what they can carry, while iron in any form doesn't cross. Thanks to the strange circumstances of his birth, Joshua Valienté is a natural. The transEarth Institute, a wing of the huge Black Corporation, offers him a job exploring and reporting on the new worlds. His partner in the enterprise will be a zeppelin inhabited by Lobsang, a distributed artificial intelligence whose human component was once a humble Tibetan. Meanwhile, back on Datum, the original Earth, officer Monica Jansson grows increasingly concerned about the anti-stepping rants of powerful demagogue Brian Cowley. Thousands of steps from home, Joshua runs into another independent-minded stepper, Sally, who turns out to be Willis' daughter. They visit a community, Happy Landings, founded thousands of years ago by natural steppers and trolls, gentle hominids who communicate via music. But both trolls and their viciously homicidal cousins, elves, are step-fleeing toward Datum from something very scary indeed. This often intriguing development of a science fiction trope takes a scattershot approach and could have used more of Pratchett's trademark satire and Puckish humor.

Still, the authors have plenty of fresh insights to offer, and fans of either will want to tag along and see where it all leads.