Oscar-winning actor and director Ustinov has always been at his best as a raconteur, whether spinning his own story (Dear Me) or other people's (Romanoff and Juliet, The Loser). But the two novellas in this slender volume aren't likely to win him many new admirers. To be sure, each is full of the sly humor we expect of Ustinov. ""The Disinformer,"" the stronger of the two, begins with a deliciously naughty premise: retired intelligence-officer Hilary Glasp, ""on a sudden impulse,"" claims responsibility for the bombing of a London shop in the name of a fictional Arabic terrorist group, the Martyrs of the Seventeenth of September. Then when the Brotherhood of the Crescent Moon, headed by Hilary's old acquaintances Ahmed Kress and Farouk Hamzaoui, also claims responsibility, Hilarycalls them in Beirut, goads them with the specter of the Martyrs, rents an office traceable to the Martyrs across the street, and sits back to await results--which involve him in amusingly unexpected ways (his apartment ends up as the site of a shootout; the police congratulate him for what turns into a free-lance anti-terrorist coup; and he finds himself reluctantly honored by the Queen before the inevitable final twist). ""A Nose by Any Other Name,"" equally witty and more deeply felt, tells the story of Thamar Atoulia's attempts to escape her stifling parents (whose well-bred domination of her is shown by the piano trios she's forced to complete) by getting herself a nose job for her 21st birthday; but here Ustinov's invention flags, and the conclusion is flat and predictable. Effervescent, funny, sad, and very, very slight.