Mother & son flee step-father with an airstream trailer; machine that can change printed text

Read a book about 30 years ago that had a boy and his mother fleeing his step-father. Much of the story is told in flash-backs so it is not readily apparent why they are fleeing. They go to his grandparents’ home and borrow a trailer. Pretty sure it is an airstream (talked about the shiny aluminum). I remember at one point, the boy befriends a young, female librarian, but they have to move on. They later encounter her again and I recall the boy being impressed by how well she handled the trailer (it had been a big deal that it was difficult to back up with it).

SF element: during one of the flashbacks, the boy had an argument with his step-father and later goes to read a book (his favorite?) and there is now a passage in it that is addresses him directly discussing how he was wrong with his argument. The step-father is involved with a group that has some machine that can change the printed word to whatever they want.

Additional details I’m not certain of: seems like the “machine” involves nanotechnology and isn’t as controlled as one would wish (perhaps some incidents of wiped text and spots changed to illegible passages). I also feel like the librarian is encountered in San Francisco. I feel like the step-father was abusive and the boy is certainly upset about the ability to change books, but not sure why the mother finally fled. When re-encountering the librarian (and depending on her to move the trailer), I think the mother had been captured and they had to initiate a rescue plan.