Paul Robertson 
According to Their Deeds [EPUB ebook] 

Charles Beale lives happily in the shadows of Washington, D.C., as a respectable rare-books dealer. Or mostly respectable. He has a streak of the gambler in him and when a devoted client dies–a man deeply connected to the Justice Department–Beale eagerly regains the man’s book collection…and soon finds himself with more than he bid on. In one volume, Beale discovers documents incriminating a host of major political figures–blackmail material that might have led to murder. Weighing questions of justice and mercy–and with a bull’s-eye on his back–Beale must untangle a complicated knot of deadly lies and dangerous secrets.