The Invisible Enemy
from School Library Journal
In this sequel to The Invisible Day and The Invisible Harry, sixth-grader Billie Stoner's enemy, Alyssa, steals her backpack on a class trip to the Cloisters in northern Manhattan, snoops through her stuff, and uses up an entire dose of Vanishing Powder. The invisible Alyssa, now more beastly than ever, forces Billie to help her return to normal, but not before they spend a torturous night at Billie's home, right under the nose of her librarian mom. The only person who can make the girl reappear is the brilliant high-school student who invented the potion and its antidote, which is made of something foul (including dog food and bubble-gum juice). This story focuses on the girls' relationship and gives possible cause as to what makes Alyssa so nasty. It is slow in parts, but fans of the previous books will enjoy the contemporary lingo and identify with the middle-schooler's angst over friends, family, and boys. Carter's amusing, full-page, black-and-white wash illustrations are scattered throughout.