Ruminator Books, a Twin Cities institution and a nationally known indie bookseller, is closing its doors forever this week, but the man who has steered it for its entire 34-year life insists that he isn’t despairing. In fact, David Unowsky admits that it wasn’t competition from big chain bookstores that drove the store into insolvency, but a series of business mistakes and good ideas implemented at the wrong time. “One of his problems was running a 21st-century bookstore on 30-year-old ideals.”