Fowls For the Times - The History and Development of the Orpington fowl by W. Cook Originator of the Breed. 165pp + 30pp advertisements.
First published in 1896, this book is written by the man who created the Orpington Breed.
W. Cook set out to create a breed of Chooks that would be hardy in all climates and serve as good egg producers and table birds.
If you are interested in what the original breed was created from, the standards that should be met with the breed, then this is the book.

The ORPINGTON FOWL by W. Cook 1896