Hi Carl,
Sure, a couple of good books are, "Keys to Successful Landcape Painting" by Foster Caddell - an older book (1976) and also "Painting Better Landscapes" by Margaret Kessler - a modern book. Of the two, the Caddell book is the best as it shows a poor and good example for each principle he examines. There are surely other good ones, but this may be a good start.
Actually, if you can't find either of these books, any large bookstore should have books on landscape painting - look for ones that closely examine composition. These lessons are usually directly applicable to bonsai composition.
Hope this helps.
Kind regards,
Andy Rutledge
b u n j i n | d e s i g n ::
www.bunjindesign.com
zone 8, Texas