So Say The Fallen by Stuart Neville Soho Press, $26.95, 325 pages, ISBN 978-1-61695-739-1 An often explored mystery theme that never seems to get old, is the question of suicide or murder. What better way to get away with it than staging the death scene and making it look like the decedent took his or her own life? Do it artfully enough to foil detection, write up a goodbye