The final Toby Peters Hollywood whodunit from the Edgar Award-winning author is "a marvelous magic trick of a mystery" featuring Harry Blackstone (Booklist, starred review).   When an anonymous rival demands that master illusionist Harry Blackstone reveal his secrets on stage or die, the magician hires Toby Peters and his brother, ex-cop Phil Pevsner, to run security for his show at the famous Pantages Theater in Hollywood. Of course, Peters doesn't expect the job to include replacing a showgirl for Blackstone's show-stopping sawing-a-woman-in-half trick after the saboteur has stolen the blade.   Peters's brief career in magic is only the first surprise as a blackmailing con man turns up shot in a dressing room backstage and one of Blackstone's competitors ends up dead at a testimonial dinner. With "The Great Blackstone" now a murder suspect, the sleuth will need to pull a rabbit out of a hat to solve this mystery . . .