“The Long Utopia” by Terry Pratchett & Stephen Baxter (2015)

“In February 2052, in the remote Long Earth…”

Back to the Long Earth for the fourth time. Spoilers ahead if you’ve not read the first three.

It’s now the 2050s, and Joshua Valienté has just turned fifty, celebrating his birthday with a trip back to Datum Earth to find out more about the father he never knew. With sentient AI Lobsang now, for all intents and purposes, dead, he wanders with fewer goals, watching as humanity evolves on these new worlds, developing new societies.

However, on a far-d...