Natasha, Pierre & The Great Comet of 1812 is a sung-through musical adaptation of a segment of Leo Tolstoy's War and Peace written by composer / lyricist Dave Malloy and directed by Rachel Chavkin. It is based on Volume 2, Part 5 of Tolstoy's novel, focusing on Natasha's affair with Anatole and Pierre's search for meaning in his life.

Based on this passage, who wrote natasha pierre and the great comet of 1812? Let's give stream of consciousness first:
The relevant information to answer the above question is: Natasha, Pierre & The Great Comet of 1812 is a sung-through musical adaptation of a segment of Leo Tolstoy's War and Peace written by composer / lyricist Dave Malloy and directed by Rachel Chavkin.
So, the final answer is composer / lyricist Dave Malloy.