In 1975 Leigh Brown had her own book published by Mason/Charter Publishers, Inc., New York. This appears to be the only book written by Leigh. I heard of a reference Shep made once about Leigh being an author in her own right. I was able to track down a copy of it in a local library.
The book is a work of fiction and centers around the world of horse-show jumping. According to the back flap, Leigh was at one time a professional rider.
The back flap also mentions her work for Shep and the dedication is no surprise.