From the longer Wikipedia article 
The Sunne in Splendour is a historical novel written by Sharon Kay Penman. Penman became interested in the subject while a student and wrote a manuscript that was stolen from her car. She rewrote the manuscript which was published in 1982.
As a student, Penman researched and wrote The Sunne in Splendour that chronicled the life of Richard III. When the 400-page manuscript was stolen from her car, Penman found herself unable to write for the next five years. She eventually rewrote the book and by the time the 936 page book was published in 1982 she had spent 12 years writing it, while practicing law at the same time.
The Sunne in Splendour is about the end of England's Wars of the Roses. In the book, Penman characterizes King Richard III as a good, but misunderstood, ruler. She chose to write Richard's character this way after becoming fascinated with his story and researching his life, both in the US and in the UK, which led her to believe that "his was a classic case of history being rewritten by the victor". Penman rejects the common belief that Richard killed the "Princes in the Tower," the sons of his brother King Edward IV, and attributes their deaths to the overly ambitious Duke of Buckingham.