This now classic book was first published by Atheneum in 1966. It was selected by Scholastic Books for inclusion in the Arrow Book Club.
From back cover:
"You must be very careful Harry!" The strange Mr. Mazzeeck warns before he leaves. "this magic oil is extremely powerful. And re,member: no one must ever find out!"

"Find out what?" Harry wonders now. Carefully he rubs the oil into his shoulders, and feels a strong tingling sensation. He rushes to the mirror and sees them-spreading out behind him, from his head to his ankles!
"Wings!" Harry gasps. As he fans them slowly, he feels himself lift off the ground.
"whoopee!" he shouts. "I can fly!"

You'd think that someone with a name like Harry Houdini Marco would be deft and skillful, but Harry could only occasionally catch even an easy fly ball without making some dumb error. On top of that, most of his friends' families were moving to the suburbs. It would have been a long, dreary summer, but then a Mr. Mazeeck showed up and turned out to be more than he seemed.