The plight of independent bookstores in the age of Amazon seems simple: live or die. But the Jan. 31 closing of BookBar, a drink-and-read concept that opened a decade ago in Denver’s Berkeley neighborhood, is more complicated. Various forces, from burnout and a minimum wage increase to owner Nicole Sullivan’s growing nonprofit and her other bookstore, The Bookies, have made it impossible to continue running BookBar, she said. On top of that, Sullivan has become controversial in the world of bookselling.