Enligt den andra personen som tittar för samma bok, Wordchanger av Mary Haynes.
An update, having read Wordchanger this evening:
- The device does use neutrinos, but only affects books within some (unspecified) radius of the device itself, not all copies everywhere. It's never explained how the device is controlled. (Updike's poem doesn't appear in the book.)
- The protagonist is 12 years old, but does at one point briefly drive a car towing an Airstream trailer. The other protagonist, whose story is interleaved for the first half of the book until she joins up in the middle, has a librarian friend who drives the trailer in reverse, having acquired this skill driving the bookmobile. The two protagonists aren't siblings, but might as well be.
- A passage in "Carry on, Mr. Bowditch" is changed, and the protagonist's name is changed on his passport.
- The antagonist is indeed the stepfather (plus vaguely threatening men from a secret government agency).