In a book to compare with his recent Spain, Mr. Sitwell writes another studied national portrait with the delicacy and strength that gives the portugal of subtle colors, of gentle chivalry and of colorful history, its due. Working his way northward on an imaginative journey that makes readers a part of a trip, there is a first stop at the southern island of Madeira. There the flowers amaze and excite, the sea life stems from a whole tradition. As one continues to Lisbon the world is one of more sense impressions- of street vendors crying in counterpoint to the tinkle of a wine glass at a polished restaurant; the more remote stillness of nearby Sintra and Queluz with their handsome residences and their occasional traces of medieval castle. Adding depth to sight and sound, taste, touch and smell is the background of history and custom and character, each quite fully realized in the course of skillful travelogue. Mr. Sitwell's consciousness of the intangibles does much to recreate Portugal as the country lacking the tragedy of Spain, whose beauties are more soft than dazzling yet whose golden era started new world discoveries. As the journey is completed in the north there is a select, rewarding oneness.