This is an excellent book; the author is uneven (to my taste) some of his series are excellent and others are scarcely worth reading - however this book - really a series in one cover is one of the better ones
The hero, is a martial arts expert, a former special forces warrior - has a strange background - for a start his martial arts style is an alien one, aliens who had gone to war with humans - and then vanished.
Now a bounty hunter, he tries to avoid complications - he does his job and doesn't get involved - or at least that is his aim, but somehow he often seems to get involved protecting the underdog. In a different genre, he would be the cowboy who rides into town, sorts out the 'baddies' and rides on into the sunset.
I enjoyed reading this book