Ralph has a real talent for expressing highly technical ideas in a way that's still accessible to the average computer nerd. Despite his knowledge and status, he's also a very nice guy and has politely answered my silly questions anytime I've asked. I'd be absolutely thrilled if the book was published.
Since you have already corresponded with him in the past, please contact him again and beg him to release his revised book, even if it is only an Online release, to save on publishing costs and reduce his risk to almost nothing.
Even if he does not want to have anything to do with the project, he could hand it off to some other person that he trusts for a small percentage of the sales generated and make a profit for himself with little or no effort on his part.
It is a real shame that he has decided to hold back this work of his when there is obviously a demand for the book and the only persons he is hurting is not the pirates that leaked any work to the Internet, he is just hurting his Amiga user fans that are clamoring for this book to be released.