This was a short-lived series initiated by Robert Skimin which, after a few books, switched hands to the now-late Mark K. Roberts. I can’t honestly say that I’ve read any of them thus far, but there is an interesting story behind this that I can now tell you.
SOLDIER FOR HIRE only went 8 or 9 books, I believe. Mark Roberts had told me that the Kennedy family (yes, THOSE Kennedys) apparently got wind of a Ted Kennedy insult that was written into one of the books (by Mark). According to Mark, a Kennedy Family representative made a call to the publisher, Zebra Books, and effectively killed the series because of it.
I asked a Zebra editor later about this and he remarked that the Kennedy comment was taken out of the book simply because it was in bad taste. The series was killed only because it was not meeting sales expectations.