I wrote a book on AIDS shortly after its appearance, but never published. People really don't want to hear the facts about this topic.
So I started a new book on osteoporosis, osteomalacia, and osteoarthritis. It is not your typical take glucosamine and chondroitin garbage type book. I go in to detail about the anatomy and physiology of bone and cartilage, and explain the purpose of each nutrient, how bone forms and breaks down, why bisphonate drugs actually weaken the bones, etc. It is about 2/3 done and I may actually finish it one of these days :-)