Finding it on rapidshit & co does not add credibility at all though. At first I thought it might be a copy from questionable sources.
Now, I downloaded it and had a look: it's a HTML e-book which is nice. It looks different from the usual ripped off e-books. I couldn't find a date so I don't know how recent it is. Also, at first glance I could not find out how to contact the author, i.e. for feedback, corrections.
Furthermore, there does not seem to be a license attached so I don't know if I am allowed to "use" the book or distribute copies. In times like these where publishers and distributors are suing people left and right, I want to be sure I won't get into trouble by using or copying the book. Again, I only skimmed the book, I did not read it fully.
Maybe I didn't see the license and contact information because I wasn't using the preferred internet explorer to view the book. Maybe I am getting blind.
If the book is free or even put into public domain, it should say so; if it is not, it should say so as well. I am super touchy when it comes to copyright, licenses, copying, distributing.
It looks like a decent compilation though...