Luna and the Hollow Hour. The Puddlebrook Tales, #3

In the quiet, unmapped village of Puddlebrook-an "Apex Point" where the membrane of reality wears dangerously thin-nine-year-old Luna Finch lives as a dedicated "noticer" of the world's hidden anomalies. Alongside her eccentric, clumsy owl companion, Waffles, Luna relies on her unique ability to observe the magical irregularities that everyone else misses. The story's true mystery begins on an impossible night when the village church clock chimes a forbidden thirteenth time.
Instead of moving forward, the world stops mid-tick, and a doorway manifests directly on Luna's bedroom rug. Stepping through, she enters the Hollow Hour: a quiet, grey, liminal dimension constructed out of lost breaths, unfinished sentences, and the forgotten remnants of the "Long-Stopped Children."Deep within this eerie gothic expanse, Luna encounters Mira, an "Echo" or shadow-version of herself woven entirely from her own could-have-been.
Luna discovers that the Hollow Hour is overseen by the Clock-maker, a mysterious entity orchestrating the temporal realm, alongside a peevish, fading ancient deity who steals fragments of reality to maintain a congregation.