The Long Earth by Terry Pratchett and Stephen Baxter

What if almost everyone suddenly discovered they could step sideways to a parallel world. What if there wasn't just one world but any number of them. Everyone can have their own private world with all the resources in it. This collaborative novel explores that premise in a simple approachable way and it makes for a very entertaining read. In order to keep things under control (and easy to comprehend) these worlds are linked serially each to two neighbours. Most people need a simple device (a stepper) to swap between them and it takes them some time to traverse more than a few worlds. Settlers set out on epic convoys to travel to far distant worlds like pioneers of the American West. Joshua Valente however is a rare individual who can step without the aid of any device and he can travel much farther and much faster than others. He sets out with an inquisitive AI to discover just what surprises lay in store millions of worlds away from datum Earth.