Gr 4-8 --Who wouldn't want the ability to undo a mistake, an accident, or even a tragedy, after it happens? Once he has the Unner, a makeshift creation of old parts and electronic gizmos, middle-schooler Gib Finney has that power.... While Gib is the only fully developed character, the unique and interesting plot featuring a practical look at the possibilities and results of planned time travel make up for the otherwise shallow characterizations. As the story gathers speed, suspense builds to a surprising and satisfying conclusion with room for more than one sequel. The book's themes and plot twists take it beyond the conventional, resulting in a delightfully thought-provoking science-fiction story.

Etchemendy... mixes quick action and long thoughts in this tale of a lad who discovers that changing the past is a tricky business. When a gimpy old man, smelling of ozone, pops up from nowhere and hands him a palm-sized time machine, Gib Finney is understandably dazzled by the possibilities. But his excitement changes to anguish.... Gib’s increasing desperation, as he tries to figure out how to head off what he knows is about to happen, injects suspense into the story, and his misadventures with the “unner” prompt insights into how minor incidents or casual choices often have far-reaching, unpredictable consequences. ... (Fiction. 10-13)

Gib is given an opportunity to change the past so that a horrible accident will be averted. ... [His sister] gets hit by a truck. Luckily, a crazy old man has given Gib the Unner, the power of time travel, to go back in time and change what has happened. When Gib goes back and tries to undo his sister's accident, he ends up changing other outcomes as well. ... This would be a good book to use to discuss choices and a good choice for any philosopher-students in your school. Recommended.