Bill and Joel read Tom Stoppard's The Coast of Utopia, which is a trilogy of plays about mid-19th century Russian thinkers! The Broadway production still holds the record for the most Tony awards won by a play. Spoiler alert: one of us didn't like this one very much!
Bill and Joel also read a big chunk of Isaiah Berlin's Russian Thinkers, which is the book that helped inspire the Stoppard.
