WHAT DOES JOAN SAY? <i> by Joan Quigley (Birch Lane Press: $17.95; 218 pp.) </i>

Latest in the spate of books on the Reagan presidency is the memoir of the woman who determined most of the President’s schedule and personal movements during his years in the White House: Nancy Reagan’s astrologer. This is the woman to whom, according to former White House Chief of Staff Donald Regan, the country owes “a vote of gratitude”; considering her influence over the Reagans, he implied, we are fortunate that she was interested in “nothing but astrology.”

When Regan broke the news of the First Couple’s reliance on astrology in his own book, the newspapers were filled with ludicrous descriptions of affairs of state scheduled, rescheduled and postponed according to the stars’ messages delivered through Joan Quigley; here we get the explanations behind her advice.

Perhaps the best insight we get into the Reagans from this book lies between the lines in Quigley’s descriptions of the business transactions between Nancy and Joan. Their first official from-the-White-House consultation occurred after the assassination attempt on the President, although Quigley contradicts Mrs. Reagan in asserting that they met through Merv Griffin as early as 1973. Quigley quotes Nancy as saying (after determining that Quigley might have prevented the attack had she been studying the President’s chart): “I’m getting terrible press. It’s so unfair. I’m really a very nice person. Can you tell me what to do? I’m willing to pay you.”

In her own words, Quigley professes to be interested in much more than astrology. In a chapter deliciously entitled “The Chemistry Between Ronald Reagan and Mikhail Gorbachev,” she takes credit for Reagan’s change of heart toward the “Evil Empire”--thereby doing her own bit toward the development of glasnost , she does not hesitate to claim. Quigley also asserts that when the Iran-Contra affair broke, it was on her advice that Reagan pursued the very successful policy of refusing to go public to defend his policies; the position of the stars, it seems, was inauspicious for explanations.

Only two categories of readers could truly delight in this book: dyed-in-the-wool cynics who can laugh at this debasement of the political process, and amateur astrology buffs, whose passions get such a stellar airing here. Even Quigley’s fellow professionals must look with mixed feelings on this unparalleled endorsement for one of their brotherhood.