I think they go Fletch, Confess Fletch, Fletch's Fortune,Fletch's Moxie, Fletch and the Widow Bradley, Fletch and the Man Who, Carioca Fletch, Fletch Won, Fletch Too and Son of Fletch. Even the early ones are out of chronology which was confusing. Fletch and the Widow Bradley takes place before Fletch. Carioca Fetch takes place immediately after Fletch.
IIRC the charcter Flynn is introduced in Confess Fletch and then went on to have his own series.