Charles Stross began his series of six alternate-timeline novels, The Merchant Princes, in 2010. A spinoff series featuring Miriam Beckstein’s daughter Rita began with Empire Games in 2017. Invisible Sun (2021) tidies up most of the plotlines but leaves just a hint of wiggle room for another series. Timeline One was well and truly nuked in the original series. Now there are aliens in an empty world and a runaway English princess aided by Rita and her grandfather Kurt, an undercover agent for the defunct East German state. The whole thing is enlivened by a steam-punky space race, nifty e-ink tattoos, and some alien hardware best left alone. I much prefer this series to Stross’s latest foray into Lovecraftian satires. ( )

Finishes the second trilogy in Merchant Princes—finally, a lot of stuff happens. To wit, the political transition in the not-like-us timeline occurs and it is very eventful and dangerous; the princess tries to avoid capture by the authoritarian US in “our” timeline; and the aliens who destroyed the people who created timeline switching in the first place have found us. Stross could have used an editor to tighten up on all the repetition—it reads like a serial, where each chapter reminds us of what went on previously—but I like the series’ heavy-handedness about the mistakes that governments routinely make about others’ intentions, capabilities, and knowledge. ( )

This is totally a last act. We know the players, we know the scenes, and we move through the set pieces to get to and ending that seems somehow too easy. As a reward were given a few pages on the Forerunners and their enemies and how the 3 worlds we spend the most time in branched off, first one then the other. ( )