"Frances Steloff: Memoirs of a Bookseller" is a wonderfully dynamic portrait of an American cultural heroine. Now 100 years old, Frances Steloff was the founder and force behind the renowned Gotham Book Mart of New York City, a center for avant-garde literature and literati since 1920. She began with only $100 and thirty books and she modestly recalls her role in the bookstore's past.