For some time now
The page has also text statistics, including various redability indexes (where it doesn't perform that well), complexity of words and sentences, total size (the book has a whopping 2,195,725 characters), and relative price: you pay one dollar for 9,011 words. Not too bad!
Speaking of Delphi books, Nick Hodges recently posted an interesting blog entry on the topic. He praises mine and Xavier's recent books saying you don't need much else, claiming that "there doesn't need to be that many good Delphi books out there". This might be partially true, and I appreciate his words ("If you have Marco's book, for instance, you really don't need any other books."). However, things are more complex. My book is selling OK, but it will probably sell a quarter of the copies it did a few editions back. There are many reasons for this (people bought earlier versions, people now know Delphi, there is so much on the web...), but overall if writing books turns in much less money, authors aren't really encouraged!
I fully agree with Nick, the publishing model needs to change. And I have actually already signed up with lulu.com (one of the sites Nick mentions), looking forward to publish soon both ebooks and print-on-demand books with them. As authors/self-publisher royalties are many times than with traditional publishing, it might be economically worth writing even to sell a few hundred books. Stay tuned.