Perhaps you're right, but if I was going to release a book and put my name on it, I would want it to be designed by a professional. Books are definitely judged by their covers.
For his last book, Tim actually printed out fake bookcovers, placed them on books in bookstores, and sat around and observed how much attention each cover brought (source: http://vimeo.com/3934635) . A lot of people around here don't like Tim, but that is certainly hacker like behavior. I'm sure he'll do something similar for the new book as well.
An anti-spec person would say, "it's so true that you need books to be designed by professionals, so that they all the technique and language of graphic design to their fullest and match the content of the book perfectly, so as to sell as many copies as possible, that you should be prohibited from soliciting the services of designers who might not meet those standards, as evidenced by their willingness to accept substandard contractual terms".