The reason that I had to write a PayPal backend is that the publication of Thinking in C# has been delayed until something very close to the end of the year. The reasons have nothing to do with the content of the book, which is very frustrating, but these things happen. In the meantime, I'm planning on experimenting with charging for a downloadable pre-publication version from www.ThinkingIn.NET. The free preview generated on the order of 100,000 downloads over the past five months, so I hope that by charging people a few dollars for the download of a complete, 1000-page, 300-working programs text, I can generate, oh, I don't know, \$20 or so.