Nishikigoi Manual of Diseases & Varieties
The Nishikigoi Manual of Diseases & Varieties contains a brief history of koi and details koi health, beautiful quality photographs, and concise information in both Japanese and English.
There is a detailed section on remedies, some of which are not contained in other koi health books.
The author, Mr. Kuroki was the long time president of the Japanese Koi hobbyist organization, the Zen Nippon Airinkai association. This text should be on every serious Koi hobbyist's bookshelf.