Author Mark Kurlansky tells the story of the time he met legendary newsman Walter Cronkite. Cronkite greeted him with the line “I know you. You’re the leading expander of minutiae.” If you’re only familiar with Kurlansky’s book titles that may seem an apt description. His latest is “Paper: Paging Through History.” But he begs to differ. He says he’s not trying to find the obscure in minor details. He’s looking for critical keys to history.