Artists are everywhere, from celebrities showing at MoMA to locals hoping for a spot on a cafe wall. They are photographed at gallery openings in New York and Los Angeles, hustle in fast-gentrifying cities, and, sometimes, make quiet lives in Midwestern monasteries. Some command armies of fabricators while others patiently teach schoolchildren how to finger-knit. All of these artists might well be shown in the same exhibition, the quality of work far more important than education or income in determining whether one counts as a "real" artist.

In The Work of Art, Alison Gerber...