RAYMOND CHANDLER'S UNKNOWN THRILLER THE SCREENPLAY OF "PLAYBACK" (Mysterious: $15.95). For better than 35 years, this screenplay by Raymond Chandler, one of America's greatest mystery writers, lay hidden in the archives at Universal Studios. Unfortunately, its publication does nothing to enhance his reputation. Chandler had already proven himself with novels like "The Big Sleep" and "Farewell My Lovely," and screenplays like "Double Indemnity" and "The Blue Dahlia" when, in 1947, he made the deal with Universal to write "Playback." It is the story of an alluring young woman with a dark secret who flees to Canada. A gigolo-hustler tries to seduce her and is found murdered. A gangster tries to protect her but only makes things worse. The investigating officer falls in love with her and may lose his job for it. There's blackmail, another murder, jealousy and intrigue, and a climactic boat chase off the coast of British Columbia. While there are occasional bits of crackling banter, and some excellent sketching of minor characters, "Playback" fails to grab. It lacks a strong central character--someone like Chandler's private eye, Philip Marlowe--to lead the reader through the mean streets. A few years after the screenplay's demise, Chandler used elements of it to create the novel that bears the same name. In the book, Chandler placed Marlowe at the center of the action.