The wild party at the Imperial Theater known as Natasha, Pierre & The Great Comet of 1812 is not your usual samovar affair. This entertainment, referencing 70 pages of Tolstoy’s masterpiece War & Peace, has its own backstory: two downtown versions had the performers mingling among the guests, diners at a banquet. While that novelty is not repeated on Broadway, the audience is privy to the gesture. The Imperial Theater is converted to a kind of supper club, music at center, with tables all the way to the stage, although the staging is not distinctly separated from the theater’s ample front area. Ramps just about everywhere allow the company to enter and exit, and dance, offering—throwing-- boxed knishes to those strategically seated. Small bars serve vodka at intermission. A coffee table sized book describes the journey of this new musical to Broadway.