Comparisons are invidious, but Hugo Hamilton is clearly a successor to the late Frank McCourt, author of the celebrated “Angela’s Ashes,” in the tradition of Irish memoir.  Hamilton read from his book, “The Speckled People,” as part of the PEN World Voices Festival on May 3. The event was held at Ireland House, a handsome mews building off Washington Square Park that is home to NYU’s Irish studies department. Hamilton was introduced by John Waters, head of the university’s Irish literature program.