""Some Unpublished Letters of Henry D. and Sophia E. Thoreau: A Chapter in the History of a Stillborn Book"" is a collection of letters written by the famous American author and philosopher Henry David Thoreau and his sister Sophia. The letters were written between 1839 and 1844, and were intended for a book that was never completed. The book was to be a collection of letters written by the siblings to each other, and would have provided insight into...