The Seer of Shadows (paperback) Avi

Horace Carpetine does not believe in ghosts.

Raised to believe in science and reason, Horace Carpetine passes off spirits as superstition. Then he becomes an apprentice photographer and discovers an eerie—and even dangerous—supernatural power in his very own photographs.

When a wealthy lady orders a portrait to place by her daughter's gravesite, Horace's employer, Enoch Middleditch, schemes to sell her more pictures—by convincing her that her daughter's ghost has appeared in the ones he's already taken.

It's Horace's job to create images of the girl. Yet Horace somehow captures the girl's spirit along with her likeness. And when the spirit escapes the photographs, Horace discovers he's released a ghost bent on a deadly revenge. . . .