On the cover of “Too Long Ago,” there is a black-and-white photo of the happiest 4-year old boy you can imagine, holding his great-uncle’s hand at the latter’s bar in Amsterdam, New York. That boy is now the deservedly heralded presidential author and biographer, David Pietrusza. Today, Pietrusza’s default facial expression is “business somber” (he appears more than occasionally on C-SPAN), and his memoir indeed explains the “stoicism” of many Polish Americans, an immigrant group whose odysseys and impressive successes in America haven’t gotten enough attention. Yet Pietrusza has written an unsomber recollection of growing up in Amsterdam, New York, with affection, appreciation, and tongue-in-cheek observations of how his city and the United States operated in the 1950s and 1960s. “A vanished world,” he writes, right on the book cover. Pietrusza admired noted raconteur Jean Shepherd, whom I got to know a bit during my early career years in New …