When I Was Old

by Georges Simenon. Harcourt Brace Jovanovich, $8.50. During three years of the kind of middle-aged melancholia that drives weaker men to the bottle or the divorce court, Mr. Simenon merely kept a journal. His do-it-yourself therapy has resulted in a book of considerable interest, not for profound thoughts or startling revelations, but for the lucid description of very ordinary anxieties.