Terry,
You asked how I know his books are at Books on Board. I use AddAll (
http://ebooks.addall.com/). Enter the author and title name, and it gives you all the main ebook merchants who carry the book in question. It's very useful.
By the way, I see that CyberRead is offering Leonard's
10 Rules of Writing for US$11.95. I think he'd be very amused at that. I heard that he was at a writers conference, and was asked at short notice to give a short talk to fill in for another speaker. He jotted down the "10 rules" on a scrap of paper, and used that for his presentation. As he was leaving the platform, a journalist asked him if he could keep the piece of paper. Leonard agreed, and the journalist turned it into a full-length article. So, now it's an ebook as well.