FLORENCE

''Florence is the only European city I can think of whose most famous citizens, at least in the last 150 years or so, have all been foreigners.'' Thus David Leavitt writes in this lively account of expatriate life in the city of the lily. His narrative begins by asking why Florence has always proven to be such a popular destination for suicides, then moves into an analysis of what makes the city, in Henry James''s words, such a ''delicate case.'' Why, for instance, has Florence always drawn so many English and American visitors. (At the turn of the century, the Anglo-American population numbered more than 30,000.) Why have men and women fleeing sex scandal traditionally settled here? What about Florence has made it so fascinating and so repellent - to artists and writers over the years? Moving between present and past, Leavitt''s narrative limns the history of the foreign colony from its origins in the middle of the nineteenth century until its demise under Mussolini, and considers the appeal of Florence to figures as diverse as Tchaikovsky, E. M.Forster, Ronald Firbank, Mary McCarthy, Mrs Keppel (mistress to King Edward VII) and Henry Labouchere, author of the Labouchere Amendment, under the provisions of which Oscar Wilde was convicted.