Dark Fire by C.J.Sansom

A historical mystery novel featuring lawyer Matthew Shardlake as a reluctant investigator for Thomas Cromwell into two murders that involve secret military weaponry, the 'dark fire' or 'Greek fire' that can burn even on water. London in 1540 is well drawn, although the various characters involved in a plot against Cromwell are at times hard to sort out.  Very enjoyable on both the history and mystery levels, and Shardlake is a strong character.  498 pg.