Clawback (Silas Cade) by Mike Cooper

Silas Cade is one of those characters that's not an official PI but is clearly a Son of Spade. This solo operative works as an ''accountant with a gun'', solving Wall Street's problems by force. When financiers are getting killed Silas Cade is hired to find out who is behind the killings. Helping him is Clara Dawson, a blogger who ends up falling for his charms. Quickly a private security firm gets involved and the action really starts. As a mystery there's not much to this novel, but as an action-packed thriller it works. Cade is a formidable hero but with a very human face and outlook on life.

The ending is quite surprising and I'm curious how his story will continue.