Pretenders to the throne of the recent detainee are legion, and what sounds like one of them has just been signed for a book at Stewart, Tabori & Chang. She's BriniMaxwell, whose bubbly half-hour TV show was recently transferred from public access to the Style Channel. Her specialty is translating '60s-style thrift shop purchases into decorating coups, and she is full of household and entertaining hints. The book, signed for the Abrams imprint by editor JenniferLevesque, will be called Brini Maxwell's Guide to Gracious Livingand is scheduled for October, in time to coincide with a new season of Maxwell's TV show.