I found it fairly easy to figure out who was writing what in this episodic series. If there were trolls or kobolds then it was Terry Pratchett. If it was scientific explainations of phenomena, it was Stephen Baxter. The premise of this series presented in The Long Earth is that there are an infinite number of Earths separated into dimensions. An eccentric billionaire puts the plans to a “Stepper” online and suddenly millions of people are exploring alternate Earths. Our Earth, referred to as “Datum,” becomes unglued as people immigrate to an Earth of their own. Of course, there are problems. In The Long War, governments on Datum try to establish their power across multiple Earths and control the Great Migration. They build and launch a series of Zeppelins with the ability to “step” through the dimensions. The crews of the Zeppelins encounter plenty of adventures. The premise of The Long Mars is that if there are an infinite number of Earths, there must be an infinite number of Marses. A crew lands on Mars and launches gliders that can “step” through the dimensions to different Marses. At the same time on Earth, an expedition goes as far as 250,000,000 Earths on a grand quest to explore the planet’s possibilities. This is Big Concept science fiction. If you’re in the mood for long, rambling adventures then this series will entertain you. If you prefer more focused action and plotting, this might not be your cup of tea. GRADE: C+ (for all three novels)