Five more of Krensky's proficient but insubstantial fairy tales. In the first, which betrays a consciousness several levels below Jay Williams' in the Practical Princess stories, a king devoted to inventions marries a clever, no-nonsense spinster rather than the flighty princesses who don't appreciate him--but he seems just as flighty in his way and no catch for the independent sorceress. As this story has the spinster raising ""Castles in the Air,"" the others hinge on literal interpretations of ""A Fine Kettle of Fish,"" ""The Last Straw,"" ""Too Clever for Words,"" and ""A Barrel of Fun."" They don't, however, rejuvenate the figurative meanings of the phrases. Passing diversions.