Push open the door. Maybe a bell jingles above your head. Walk inside. Sniff, look, listen: the smell of ink on paper, the glow of sunlight filtered through ivy creeping up old windows, the wooden floor creaking and maybe slightly at a slant. Maybe it is afternoon, and a couple of guys are playing chess on the sidewalk out front. Maybe it is evening, and someone is singing at an open mic. Maybe (almost certainly) there is an inviting nook in which to sit. Independent bookstores, once considered an endangered species, are on the rise — slowly, but on the rise — from 1,400 stores nationwide in 2009 to more than 1,600 last year. Minnesota has more than 50 indie bookstores, each doubling as a little neighborhood community center.