The Sachertorte romances by Ibbotson (Madensky Square, 1988, etc.) have resisted a firm categorization. The narration is too witty and waggish for the average lathering romance, and the plots too drenchingly sweet and contrived for a Fay Weldon-style satire or a Malcolm Macdonald chatty comedy. Here, the publishers have wisely allowed the author her own directive for her work: ``for the intelligent woman with the flu.'' Just so. Ibbotson's latest offering concerns the career of clever, enormously learned, and bouncy Ruth Berger, daughter of an eminent zoology professor and an excessively good mother whose house in Vienna also shelters an anthropologist aunt, alarmingly clumsy in all but her seminal work on obscure tribes, and a sad little uncle with a romantic past. Also, on the eve of WW II, another of the Bergers' summer visitors is Quinton Somerville, a young Englishman, a comer in paleontology, and the brilliant boy pianist Heini Radek. During the scholars' vacation in the mountains, Quin loves the Bergers, and the child Ruth adores just slightly older Heini. Eight years later, after the Nazis grab Vienna, Quin returns and, via a ``paper'' marriage to Ruth, rescues her so that she can join her family in a seedy section of London. The refugee colony makes do in tacky digs while Ruth, keeping secret the marriage to Quin, anxiously awaits the arrival of her fiancÇ Heini from Hungary. Meanwhile, she attends the college where Quin is the stellar lecturer, and with a group of students sees for the first time the Northumberland homestead where reigns Quin's fierce spinster aunt. Among Ruth's new acquaintances: dim-to-devoted schoolmates; dazed intelligentsia and an eccentric or two soldiering on; and, spearheading a sizable contingent plotting to wed Quin, a upper- caste student of terrifying perfection and the mien of a Roman senator. There will be misunderstandings, crossed paths--and, of course, happy endings. A bedtable joy.