by Houghton Mifflin /Peter Davison, $19.95. In addition to her great achievements as a choreographer, Ms. de Mille writes admirably. Her portraits of dancers, producers, relatives, friends, and a mad cook bring all these people sharply to life. By reflection, they reveal the author as a generous admirer of the skills of fellow professionals, a ruefully humorous observer of her own errors, a firm hater of producers, and a hopelessly soft touch. Nobody else would have tolerated that cook for a month. The chapter on the career and influence of Isadora Duncan is probably the best account ever provided of that eccentric genius. Ms. de Mille never knew Duncan or saw her in action, but her vast knowledge of dance and its capabilities enables her to reconstruct, with great conviction, what Duncan did for her audiences and for the status of dance as a serious art. Witty, informative, quietly passionate, this book is a beautiful performance..