The first full biography of Jane Seymour written by Elizabeth Norton comes in at 158 pages. Technically it is the first biography dedicated entirely to Jane Seymour, but the page count will give you an idea of exactly how much we know about Queen Jane, which is of course, very little.
She does make a challenging subject for a biography. While Jane had a place at court with both Katherine of Aragon and Anne Boleyn during their reigns, with nothing really recorded about her at the time, she seems to have been quite an unremarkable figure. That is, of course, until she caught the attention of King Henry VIII and was instrumental in one of the most infamous marriage breakdowns in history.