Spoilers ahead:
Wilson is an independent criminal contractor, who basically kills people or breaks their legs (but only other criminals). He's retired and has tried to hide himself. Unfortunately a chance news article photograph accidentally exposes him and his old an employer (a mafia boss), tasks him to find who killed his nephews and won't take no for an answer.
There isn't any subtlety in this series. Wilson uses his street smarts to find his culprits and then uses his fists or gun to subdue his victims or to obtain information. There aren't any deep thoughts or political moralizing (copied from another review). I enjoyed one or two in this series but I won't continue.
Why? Because there isn't any real character development. I read books because I like the protagonist or because the writing is smart. Wilson does have street smarts but he is basically the blunt instrument of the author who uses him to smash down or kill opponents. The Malko series is somewhat similar in that it's also simply written and action packed but for some reason the Malko series has smarter writing. I think maybe the Wilson character is too blunt for this own good. Anyway, if you like violence and don't want any frills to go with it, you may like this book.