A rummy married to a crazy""--that was Hemingway's remark about the Fitzgeralds although nothing that incisive nor inelegant appears here in Mrs. Milford's long, ladylike and regrettably styleless (she's a very slack writer) story of Zelda which is drawn from a good deal of new material and many hitherto unavailable letters. It seems too bad that much of it has not been handled with sharper effect. ""All I want is to be very young always and very irresponsible and to feel that my life is my own."" These words of Zelda's were spoken early on in her headstrong, indulged life as the youngest in a family of six children in Montgomery, Alabama--impatient, restless and defiant and as incredibly beautiful as the young man whom she first met when he was stationed in the Army down there. It seems unnecessary to fill in the known particulars of their reciprocal love and mutual devastation through the years--the fretful, extravagant, exhausting pace they pursued both here and in Europe--and their attractiveness, selfishness and competitiveness (Zelda's Save Me a Waltz and other stories are analyzed at length but not in depth if they had any)--her first breakdown which led to the second collapse and the long years in and out of institutions while Scott was equally ravaged by his debts, his drinking, his insomnia. . . . Mrs. Milford brings no really great insight to any of it and in spite of all the letters threaded between the commentary, none has the childlike, tragic eloquence of the one which appeared toward the close of the Arthur Mizener book when, estranged, they were living in very different worlds--""I love you anyway--even if there isn't any me or any love or even any life."" This is a Book-of-the-Month Club selection and its success seems well assured. The romantic incandescence of Scott and Zelda's ""fairy tale,"" however hard to justify, is equally impossible to repudiate; there will be many readers, particularly women, who will be happily submerged during the evening they've saved for that last, lost waltz.