Discoloration on book jacket Some chipping along the edges Two books in one! Dodd, Mead, 1975, 377 pages AFTER 55 years on the best seller lists, Agatha Christie remains without peer as creator of edge-of-the-seat entertain-ment. And just as Dame Agatha occupies a special niche in the literary annals of our century, so too does her fictional sleuth, Hercule Poirot, whose remarkable "grey cells" place him alongside Sherlock Holmes as one of the immortals of detective fiction. Poirot made his debut in 1920 in The Mysterious Affair at Styles. More than a generation later, he meets his final challenge in Curtain, in which he confronts the most fiendishly clever murderer of his long career. The little English village of Styles St. Mary provides the setting for both ad-ventures. In his first case, Poirot investigates the baffling death of the mistress of Styles Court, the great manor house. He returns there for his last ad-venture, to find that in the years since the Great War, Styles Court has degenerated into a “guest house.” Poirot believes that among its residents is a psychopathic killer who has already claimed five victims- the “perfect criminal “ whose technique is so ingenious that in each case, not only did he himself remain untouched by suspicion, but an innocent person stood trial for murder.