Who can say why the author of such emotionally resonant novels as Stepping and Three Women at the Water's Edge has lately been tinkering among the genres. But here Thayer's at it again, this time experimenting on the old rags-to-riches formula--with disheartening results. Granted, her heroine, Catherine Eliot, isn't exactly a pauper when she starts out, but rather the black sheep in a New York society family. After graduating from Miss Brill's School for Girls, she's cut off by her awful, Scotch-sodden parents because she refuses to go to college, making her a poor little match-girl, in effect; only her odd, reclusive, garden-happy granny, living in an East Hampton mansion, seems to care for her at all. Catherine's left to fend for herself on the streets of New York during the early 60's, where she lands a job in a flower shop, which she eventually buys with a cool hundred grand she's obtained by blackmail. Her floral emporium, called Blooms, becomes a big success. On the romance front, she fares equally well, settling down with preppy lawyer Kit Bemish. Periodic problems ensue as she tries to juggle her marriage and career; but, in the end, there doesn't seem to be anything Catherine can't handle--which is why she inherits her grandmother's estate when the old lady finally hangs up her pruning shears. Every now and then Catherine's internal life strikes a realistic note, and the floral detail is nicely done. But the rest is plastic--glitz fiction done by a pretender, and a definite turn-off for old Thayer fans.