In her art guide to five European cities, Blanche Brown has set out to explain them historically as well as aesthetically. In each case she views the total city as a work of art -- and has chosen her cities accordingly; writes of the pochs and artists each best represents; comments upon one day excursions from the center; and lists (perhaps the major part of the book for sightseeing purposes) the principal monuments and works of art to be seen. There is Athens, with its antiquities in a nondescript modern city; Rome, where ""you find your art alive;"" Florence, which ""strikes one clear note"" against Rome's polyphony; Paris, ""the most beautiful of them all,"" and London, formless, both ""ugly and lovely."" The essays are for at-home or sea reading, the lists for on-the-spot reference, but the book itself is, as the author herself remarks, too bulky for pocketing or carrying about. The excursions are barely noted, as against more orthodox travel guides, so it is the preliminary stretch in which this would appear to be helpful. Well informed.