At her awfulest, Suzanne Vale -- the same Ms. Vale of tears and bons mots from Fisher's wisecracking-through-rehab 1987 best-seller ''Postcards From the Edge'' -- stops taking her medication for bipolar disorder. She has a psychotic break, quite different from her usual state of brittle mirth as a Hollywood insider with a daughter by a fellow Hollywood insider who ''forgot to tell her he was gay.'' (She'd fit into a Bruce Wagner tale.) Eventually Suzanne is hospitalized. (She'd fit into an Augusten Burroughs tale.) Then she's released, happy for the mother-and-child reunion with her adored little girl. Fisher's prose is trademark snappy and free-associative, and, as in ''Postcards,'' she gaily courts speculation about the book's real-life models. But there is something disconcertingly blue and lost beneath the book's hectic charms, like dark circles of sleeplessness under the eyes of the life of the party.