Master Mike and the Miracle Maid (ISBN 0-03-063765-1) is a children's novel written by Elizabeth Starr Hill first published in 1967. It was re-published as a serial in the Scholastic magazine Summertime starting in the June 25, 1973 issue.
Master Mike and the Miracle Maid Wikipedia
17-year-old Mike, a comic book fan who collects strange gadgets (many of which he obtained by sending in coupons from cereal boxes), is staying for the summer with his 13-year-old cousin Penny, whose parents are getting fed up with his antics and ready to send him back home. After attending a magic show where people gain strange powers, Penny and Mike sneak onto the stage and Mike uses the magician's magic chair to cast a spell on Penny. To their surprise, it works, and Penny gains superhero powers such as strength, flight, and the ability to pass through solid objects. Penny becomes, in Mike's words, "the world's most amazing 13-year-old". She also becomes eight feet tall.
Penny's new powers lead to adventures and misadventures, and generally interfere with her normal life. Penny also resents the loss of control that comes from the powers being activated and deactivated exclusively by Mike, the spellcaster. However, Penny successfully captures a gang of crooks who were attempting a series of major thefts.
Although Penny ultimately uses her powers successfully (after some embarrassing errors), she still wishes to be normal again, but she finds out that the magic chair used to enchant her has been accidentally destroyed, so there is no way to undo the charm. Just when she despairs of ever having a normal life again, she reaches her 14th birthday; suddenly, her powers are gone, as the spell granted powers to a 13-year-old.
Kirkus Reviews stated "If there's anything duller than a comic book, that's all text, it's a poor parody of a comic book without pictures." and concluded "it's just plain tedious and trite, and no challenge to Superman."