Black and Blue Magic — Zilpha Keatley Snyder

A long, boring summer in the city stretches ahead for almost-twelve-year-old Harry Houdini Marco. Running a boarding house with his widowed mother is a never-ending job, and all Harry's friends have moved to the suburbs.

But one day he does a favor for a clumsy little man on the bus and receives a gift that staggers his imagination -- soft-feathered, cloudy-white, magical wings! A pair of wings on the shoulders of an impossibly clumsy boy spells bumps, bruises, and scrapes. Can Harry keep his "black and blue magic" a secret and still manage to find his mother a new husband?