The Principle of Moments (Order of Legends, #1) by Esmie Jikiemi-Pearson

6066: In Emperor Thracin's brave new galaxy, humans are not citizens but indentured labourers, working to repay the debt they unwittingly incurred when they settled on Gahraan - a desert planet already owned by the emperor himself. Asha Akindele knows she's just another voiceless cog working the assembly lines that fuel his vast imperial war machine. Her only rebellion: studying stolen aeronautics manuals in the dead of night. But then a cloaked stranger arrives to deliver an impossible message, and her life changes in an instant.

1812: Obi Amadi is done with time-travelling. Never mind the fact he doesn't know how to cure himself of the temporal sickness he caught whilst anchoring his soul to Regency London, the one that unmakes him further with every jump. Or if the prince he loves will ever love him back. Or why his father disappeared. He is done. Until he hears about the ghost of a girl in the British Museum. A girl from another time.

When Obi's path tangles with Asha's and a prophecy awakens in the cold darkness of space, they must voyage through the stars, racing against time, tyranny, and the legacy of three heroes from an ancient religion who may be awakening, reincarnated in ways beyond comprehension.

A love letter to Black readers of science-fantasy, The Principle of Moments is a symphonic, centuries-spanning adventure - unmissable for fans of the spacefaring found family of Becky Chambers, the alternate London of V. E. Schwab, and the virtuosic climate-craft of N. K. Jemisin.