Jessica: Chitwood’s is not bad, neither is Seager’s.
This link is to an old and incomplete biography written in 1843. It contains some primary material which may be of interest: http://books.google.com/books?id=_2HmZhfbOGMC&printsec=frontcover&dq=john+tyler&source=bl&ots=KN2xUbRbPn&sig=J7kl-rIxJGsaRis9HCjV4xD4U7I&hl=en&sa=X&ei=1bwaUMJCgpbaBY2IgPgN&ved=0CDQQ6AEwAA#v=onepage&q=john%20tyler&f=false
This link to to a three volume work on the Tyler family from the president of William and Mary College, a direct descendent. Again, it contains very good primary material. You can find the other two volumes on Google Books as well: http://books.google.com/books?id=Zl-6CVMx398C&printsec=frontcover&dq=editions:5JuYlm-ykeUC&source=bl&ots=8KnheWuzTz&sig=6bvsu_W8KETWoORiIHRMi4XdEMs&hl=en&sa=X&ei=5L0aUOC8LeLo2QX954GQBg&ved=0CD4Q6AEwAg#v=onepage&q&f=false