Buchwald's 21 st collection of satires, and something of an annual event. Therein lies his strength. For he produces so many of these little pieces that an annual edition is able to retain its timeliness, unlike some others of this ilk. Timeliness, however, is not the only criteria for holding a reader's interest. Other considerations are such qualities as originality and freshness. And here Buchwald disappoints. He has come to rely upon too many hackneyed contrivances, such as the clipped conversation with an anonymous symbol, and his almost exclusive preoccupation with political Washington. Three times per week, perhaps, one does not notice these lapses. But in a single volume, those same columns all seem to become one. Satirists such as Russell Baker, who glean columns not only from politics but from the everyday foibles of human existence, are better long-distance runners. But Buchwald has his audience and he regales them here with swipes at Reagan's tax policy, Third-World credit, female vice-presidential aspirations, Washington real-estate prices, Star Wars, and about 130 other current topics. Perhaps, in the end, anyone who can elicit a chuckle in these increasingly surly times has to be considered a valuable asset. With a little more practice, he just might get it down pat.