The Town That Went Dark. The Long Lamplit Way, #1

Some towns go dark when their light fails. Sennhold went dark on purpose. On the great slow sky-ocean of the Ondimere, where timber towns ride the warm air and the only road between them is a lane of floating lamps, Ilma Marisk keeps the light. She is a Lampwarden, and her whole craft is small and unglamorous and holy, sail the round, mend the frayed lane, coax a tired beacon back onto its seat so a town lost in the haze can still be found.
Then the post brings word that Sennhold has gone cold. Every lamp out. The last lit town before the haze swallows the Way, drifting quietly off the map. Ilma finds the town not wrecked but grieving. Its old keeper fell from the tall central mast and died, and rather than send anyone up in his place, Sennhold has chosen the dark. Least of all will they send his apprentice, a boy of seventeen who watched him fall and has not climbed since.
Ilma cannot relight a town over its own head. So she stays. She mends what her hands can reach, she teaches the boy the knots his master never got to, and she waits, light by light, for a town holding its breath to decide it still wants to be found. The Town That Went Dark is the first book in The Long Lamplit Way, a warm, low-stakes, found-family comfort series for readers of gentle fantasy about small brave work and the people who keep the light.
No peril darker than a long winter and an old grief. A hopeful ending, every book.