Related link: http://pragmaticprogrammer.com/titles/rails/
What the Pragmatic Programmers did with their new book on Rails is wonderful: they started selling it as a PDF when still in BETA - to please the eager, and get feedback/typos.
Now that I’m going through the book, this appeals to me on a few different levels:
#1 - I had a strong practical need for this book NOW - not in 5 months, but now now now. THANK YOU to the authors for making this available early. It has helped me immensely.
#2 - They have a wonderful error-submitting page that they respond to daily. I found a few typos as I was going through the examples, submitted them, and got a reply that they were fixed the following day. THIS IS BRILLIANT! Why wait until it’s on the bookshelves to find out that there are typos?
#3 - I prefer technical books on PDF anyway.
Releasing books in beta-format takes advantage of the fact that there are different kinds of readers. Some, like me, need the info sooner, even if it’s not “perfect” yet. We’re avid fans of the technology. We’ll hear on the mailing list that you are making this available. We’ll be right there giving feedback daily, which will improve the book for when it’s released to the much-larger public.
I hope more authors and publishers do this.


Re:
Interesting. In essence, this takes the principle of wiki, in a restricted form, to the book authoring process. The strenghts (and weaknesses) of wikis are well-known.
Here's another one
Peter Seibel's book, Practical Common Lisp, is available on his web site http://www.gigamonkeys.com/book/ and was discussed on the comp.lang.lisp newsgroup as he wrote it. Didn't seem to hurt the sales at all.