Martin Van Buren was something of an odd duck of a president. He was our first president to have been born a US citizen (i.e. the first elected president to have been born after Independence.) He was our only president for whom English was not his native tongue. Of Dutch heritage, he only learned English once he began attending school. He was the first president to have been elected not to have either a military commission or a university degree. He was the second president (after Thomas Jefferson) who was a widower when elected and he remained a widower during his full term as President.
I have just been told, and can find nothing to contradict the claim, that his 700 page The Autobiography of Martin Van Buren is notable for not mentioning either his wife or his presidency. Kind of an important omission it would seem.