When science fiction fans wax nostalgic for the novels of Robert A. Heinlein, they are more likely to have Stranger in a Strange Land, Starship Troopers, or his celebrated juveniles in mind than the solipsistic, arguably misogynistic books that appeared at the tail end of his career. Leave it to Charles Stross, author of Accelerando and Halting State, to find a fresh way to pay homage to late-period Heinlein in a space opera with decidedly 21st-century sensibilities. Saturn’s Children uses Heinlein’s 1982 novel Friday as its template, chronicling the solar system–spanning adventures of Freya Nakamichi 47, a femmebot designed for the carnal pleasures of her human masters. Unfortunately, humans died off two centuries ago, leaving Freya and her robotic siblings at extremely loose ends. On the run from aristocratic slaveowners with a grudge, the comely android takes a job as a courier, carrying a mysterious package in her abdomen from Mercury to Mars. En route, Freya finds herself imprinted with the memories of one of her missing sisters, falls in love with the wrong artificial person, and discovers unsettling secrets about the original model in her line. This overly complicated stand-alone novel never quite achieves the sublime lunacy or the mind-bending inventiveness of its author’s best work. But rather like the book that inspired it, Saturn’s Children offers more than its fair share of action, humor, artful extrapolation, and intriguing discourses on the nature of free will.