Currently reading One Last Kill by Barry Eisler. It's the fourth in his series about John Rain, a Japanese-American assassin.
Rain cuts a lonely, isolated figure. He has been killing ever since he served in Vietnam as a teenager. By now he has developed a professional stoicism to his profession; distancing himself from the emotional ramifications of killing; filling his world with security measures in case anyone tries to come after him; cutting himself off from anything -- friends, family, lovers -- that might make him an easier target. He is calm, implacable, trusting no one.
But as the novels progress events conspire to awaken his emotions, to stir his conscience, to revive his trust in friends. These are traits that he can do without, that can get him killed. The rediscovery of his soul could just cost him his life.
Eisler himself served with the CIA for three years so he writes authoritavely about espionage matters. He also lived in Japan which lends atmosphere to the many scenes set in Tokyo. On top of that he's a black belt in judo and currently trains in Brazilian ju-jitsu.
Eisler says there will only be six John Rain novels which suggests he has a definite conclusion planned for the series. I'm not sure whether he will finally allow Rain to retire or if he'll leave him trapped in a world of death, violence and paranoia.
But it'll be fun to find out.