She has often skirted the edges of legal ethics, but in Perri O'Shaughnessy's book, "Unfit To Practice"(Delacorte, $24.95), Nina is fighting for her license and her livelihood over a complaint that may lead to her being disbarred. One September night, her unlocked truck is stolen. When she gets it back, gone are her most sensitive files, together with her sometimes brutally candid notes on the case and the people involved.