What's the most downloaded ebook ever?

Is there a central clearinghouse that tracks the most viral ebooks and docs?
Not the trivial stuff of the Lycos 50, but ideas and argumentative pieces
that have spread quickly through the Internet.

If there is no site, can you find the things (written or graphical) that
make a point and that were passed around the Net? It could even
include long text-based emails. Also, we are looking for places on the
Web where people are talking about these types of pieces.

The ideal answer will provide us with several examples of content that makes a
point and has spread through the Web. More important, it will include
objective detail about what has spread and where to find data about what IS
spreading. It will also include names of several sites where people
discuss these types of pieces.

I think it would still be the bible.

As to the spreading of messages, the most spread message is an
encrypted code, also called a virus. Second one and sligtly older is
the WC3 html recommendation.