The Posthumous Memoirs of Br†s Cubas ($25.00; Nov.; 256 pp.; 0-19- 510169-3): This earlier (1881) novel by the prolific Machado (18391908) employs the same essential technique (stops-and-starts, authorial expostulations, direct addresses to the reader) to tell the story, following his death and written from the ``other world,'' of its amazingly blasÇ title character and narrator. Br†s Cubas, the scion of a wealthy family, while laboring to mass- produce a miraculous ``poultice'' that will guarantee the health of mankind, unwisely ignored his own and died—leaving unresolved a dizzyingly amusing farrago of personal, professional, and sexual preoccupations. The story's form, of course, recalls Tristram Shandy. Fortunately, so does its wealth of vivid supporting characters—at least one of whom, the ineffably confident ``philosopher'' Quincas Borba, belongs with his uniquely gifted creator right up there among the immortals.