“Best Sellers” (** out of four) was an only mildly endearing comic melodrama about a cranky and retired author (Michael Caine) who finally publishes his final book and reluctantly embarks on one last book and publicity tour to help out his young publisher (Aubrey Plaza). A great role for Caine who keeps film going with his usual effortless charisma but story and charaterizations are awfully thin; Caine himself played a similar role in (the better) “Deathtrap” and also “The Quiet American.” Caine has said this may be his last ever film-role at 88 but this is far from his “best.”