Twenty-three-year-old Blackwood & Brower Booksellers in Kinderhook, N.Y., is the latest bookstore to suffer the double-whammy of aging staff and book industry changes. The store will close at the end of June. In a note to New England booksellers, Rondi Brower cited the fact that her father hasn’t worked in the past year and that the downtown in her community shrank with last November’s fire, which destroyed two downtown buildings in the village. These factors combined, she wrote, to "affect the bottom line in a way that could not be ignored any longer."