What do you mean you're a participle in the school play and you need a costume?""...""So you swallowed the plastic dinosaur out of the cereal box. What do you want me to do, call a vet?"" Mrs. Bombeck has written a book about the dilemmas of the Great American Housewife and At Wit's End is a lot of laughs. The Joan Rivers of Ohio suburbia, she takes off on all the familiar homilies and then some. How would you like to be married to a ""nocturnal animal""...""who keeps resetting his alarm clock in the morning and each time it blasts off smacks it silent and yells, 'No one tells me what to do, Buddy.'"" In fact they've often made the Ladies Home Journal feature ""Can This Marriage Be Saved."" There was the time, for example, that they used guppies to teach their kids sex education and now have a son who wonders if he'll be able to hold his breath under water long enough to lay eggs. A syndicated columnist (appearing in 65 newspapers) she provides the perfect day's pick-me-up. Pick it up.