I don't understand why "Of Muppets and Men" hasn't been reprinted. There are alot of puppetry-related books that would do quite well in a limited run including Bill Baird's The Art of Puppet. I think the problem is the large publishers need to sell thousands and thousands to make a reprint economically viable. Smaller, specialty presses would be reprinting books like these and selling them like mad because they are better at selling to a targeted customer base and they know who their customer is.
As for reprinting a book, irregardless of how long it's out of print I stand by the statement that it's completely wrong ethically. What gives someone the right to publish an author's work without permission? I find the whole idea very disrespectful and wrong.