by Knopf, $3.50..
Miss Compton-Burnett is not merely original — she is unique. Like her previous novels. Darkness and Day is a glacially witty conversation piece about skeletons in the cupboards of English country gentry. The skeleton in this case is incest — not a fruitful subject for comedy. In Ivy Compton-Burnett’s hands it proves exceedingly fruitful and appallingly comic.