In 2006, when the Brooklyn Book Festival was in its first year, a panel discussion focused on how Brooklyn had shaped the writing of Jonathan Lethem, Paula Fox and Emily Barton. Pete Hamill and Jennifer Egan, both of Brooklyn, talked about their literary inspirations. Dramatic readings from the work of legendary Brooklyn writers were staged in a plaza outside Borough Hall. This year, the festival’s sixth, it remains centered in the same pocket of downtown Brooklyn. But its borders have spread far beyond.