This is an example of Generalising From One Example[1]. The author doesn't have enough information to draw the conclusions that he has drawn. In other words, it's essentially nonsense.
Why the argument can be made that a single example does not prove a point, the author nevertheless provides a description of his experience that can provide others with valuable information. Therefore, to call this nonsense is very unfair. He will learn from his experience, and by taking the time to present in detail what insights he personally gained, a body of knowledge about this subject emerges that will help others.
I agree with you there. Imagine you would be at an actual market with a pile of your books and you would tell people they can take it with them and then later decide if they want to give you a 'donation' for it. I would assume similar results can be seen.
Also going in semantics.. Demanding a 'donation' is a contradiction.
[1] A good essay on the subject - http://lesswrong.com/lw/dr/generalizing_from_one_example/