Cynthia Helms was in charge of radio programs for the Smithsonian when husband Dick was abruptly bumped from the CIA to the ambassadorship-of-his-choice, Iran, so she's not about to confine herself to foreign-service chitchat; what she can say, on the other hand, is very limited--and much of what she relates is book-knowledge. There are some obligatory remarks on the difficulties of running any embassy (e.g., lack of funds for immediate necessities--like place mats), and on ambassadorial problems peculiar to Iran--most pertinently, the inadequacy of 18- and 19-year-olds as marine guards. (A disturbed woman was one day ushered in, unchallenged, to husband Dick--""probably the most guarded man in Iran besides the Shah."") There are unassuming disquisitions on Persian culture and customs: Mrs. Helms was studying the language, attending classes on the religions, participating in a poetry seminar. And the discussion of the place of Iranian women is discriminating: the chador, we're repeatedly reminded, is ""a privilege as well as a prison."" On the Shah, Mrs. Helms is necessarily discreet; the nearest she comes to a judgment or an analysis is to say that, since he provided no outlet for political expression, ""the people had nowhere to go but the mosque."" She also notes, from trips around the country, the lack of progress in rural locales. On the personal side, there's a corresponding lack of spontaneity: once, an Iranian friend takes Mrs. Helms to the public baths, and she emerges feeling ""soft, beautiful, and magnificently clean,"" to walk blissfully along the fragrant, tintinnabulating late-afternoon streets. But such immediacy is rare. Overall the book is pleasant, smoothly written, and bland--an effortless entree and overview for the uninformed.