An interstellar craft is decelerating after its century-long voyage. Its destination is V538 Aurigae ?, a now-empty planet dominated by one gigantic megastructure, a conical mountain of such height that its summit is high above the atmosphere. The ship's crew of five hope to discover how the long-departed builders made such a colossal thing, and why: a space elevator? a temple? a work of art? Its resemblance to the mountain of purgatory lead the crew to call this world Dante.In our near future, the United States is falling apart. A neurotoxin has interfered with the memory function of many of the population, leaving them reliant on their phones as makeshift memory prostheses. But life goes on. For Ottoline Barragao, a regular kid juggling school and her friends and her beehives in the back garden, things are about to get very dangerous, chased across the north-east by competing groups, each willing to do whatever it takes to get inside Ottoline's private network and recover the secret inside.Purgatory Mount, Adam Roberts's first SF novel for three years, combines wry space opera and a fast-paced thriller in equal measure. It is a novel about memory and atonement, about exploration and passion, and like all of Roberts's novels it's not quite like anything else.