What could have been a delightful tour of three 19th-century European capitals becomes in Olsen's hands a wearisome trek through a maze of statistical and economic back streets. To complicate matters, the author's listless prose style and seemingly endless repetitiousness dampen further any enthusiasm the reader may have felt for the subject initially. Only the most dedicated student of architecture or of urban planning is likely to accompany Olsen to the end of his admittedly scholarly but decidedly lead-footed peregrinations. Basing his thesis on the differing tastes, historical backgrounds and social requirements of Parisians, Viennese and Londoners during the century preceding WW I, the author attempts to show how these factors affected the faces of the three cities. In Vienna, for example, the wealthy opted for flats in sprawling apartment buildings; upper-class Londoners preferred to settle into detached dwellings. While their English cousins demanded quiet neighborhoods insulated from the hurly-burly of the city streets, Parisians were never happier than when bustle and excitement surrounded their homes. Such obvious and overworked insights into national (or at least urban) temperaments form the rather shaky foundation upon which Olsen tries to erect his ponderous structure. As professor of history at Vassar College, the author knows his subject from basement to attic. (His earlier books investigated Town Planning in London and The Growth of Victorian London.) Unfortunately, however, he seems unable or unwilling to enliven his narrative with colorful anecdotal details that would introduce a human scale into the work. At one point, Olsen states that he is bent on emphasizing what he calls ""high mediocrity"" in the architecture of the three cities. Sad to say, he seems to have used the same standard in putting together this monument to academic overkill; 142 black-and-white and eight color illustrations do little to lighten his text.