This latest addition to Morton's long list of travel books may well be his best. ""No one in Rome,"" he says, ""ever tells you anything,"" and so he proceeds to tell practically everything about the city that can possibly be presented in one volume. From its beginnings to its present day crowded buses, restaurants and limping lifts, from popes and emperors and politicians to fountains and excavations, from churches, and ruins to pictures -- all are strung on a thread of delightful personal comment. Unlike many travel books this one is never dull nor sentimental and it is at once witty and informative, casual and erudite. In no sense a formal guidebook, it contains no starred pictures or churches, as does Baedeker, and few statistics, those few being of the informal and unexpected variety -- such as the cost of a Cardinal's hat. Professional historians may question a few of the author's statements but they cannot quarrel with the way in which he presents them nor with his reconstruction of the past. For those who are housebound or footloose and certainly to be read by all before, during and after a visit to Rome.