Her first novel, "Topping from Below, "was a cause celebre of erotic fiction. Now, in "Panic Snap, "Laura Reese once again crosses the boundary between pleasure and pain with a story of extreme sexual obsession and one family's terrible secret. The accused murderess in a sensational trial, Carly Tyler waits outside a California courtroom as a jury decides her fate: Is she the depraved Madame de Sade of the newspaper headlines or the innocent victim...