|By "meta-fantasy", i mean that this is a fantasy about fantasy -- even referencing the author's own fiction as fiction.
And it is hilarious. As soon as Susan begins reading aloud from the seven-day book that she checked out of the library on a whim... and reads the opening paragraphs of the book that the reader is already holding in his hands, we know we're in for a strange ride, indeed, even for Edward Eager, who gave us Half Magic (in which there is a magic charm which grants one-half of what one wishes; a wish to visit a desert island puts one in the Sahara -- "Desert, yes -- island, no.") and The Time Garden (in which one set of magically-adventuring children rescue another set from another of his books from cannibals).
So first read the Half Magic books (currently available as a boxed set), then grab this one and fasten your seat belts, keep arms and hands inside the car at all times, and enjoy the ride.