A FLEETING SORROW by Francoise Sagan. (Arcade: $19.95; 192 pp.) You know, almost from the beginning of this hysterical, histrionic, supremely French novel what will happen when Paul Cazavel, a robust, smug, peak-of-life architect and womanizer, is told by his replacement doctor (a man who strongly resembles a hamster in empathy and build) that he has six months to live. The novel takes you through the day he gets the news, the hours in which he is forced to confront the mediocrity in his otherwise airtight life, the cliches he perpetuates every day and the sources of real joy he has lived without. He tells his best friend, who interrupts several important phone calls to deny everything Paul tells him. He tells his mistress, beautiful but stupid, who feels her own pain (literally getting a migraine when she hears the news) so utterly that there is no room for Paul’s. He goes looking for the love of his life, miraculously available and only a few blocks away during the 10 years he has repressed the memory of her, finds her and obtains her unselfish promise to care for him in his final months. He tells his long-estranged wife, who immediately steps into the role of martyr to the cause. And then he gets the call from the hamster who tells him it was all a mistake. Alas, the reader fears, this kind of ego is hardly unraveled by a mere near-death experience.