It is an interesting proposition, but I do not know why, I feel to give out my book for free, the reason for this might be from the fact that I learned programming on my own reading free books, the great books came with a hefty price tag, hence I don't feel it morally right to publish my book/tutorial at a hefty $$.

Said tutorial/book since people have told me that if it isn't present in actual stores it can't be called a book :)

Also, my first book/tutorial is available via leanpub.com, so users can pay if they want, so far hardly 10 have paid, but gitbooks.com where the online version is hosted does get around 200 page views daily + 800 downloads monthly. Leanpub currently has 550+ readers.