Just now found out an online library was borned, the name - World Digital Library (link: http://www.wdl.org/en/).

I have click in and browse through a few books, the books are in TIF image file, it is able to download as PDF. The loading speed seem pretty decent, probably due to not many people browsing this website yet.

Finally, most of the books are historical based. So if you thinking to read the Dan Brown or Phillip Pullman's novel, you'll be disappointed.

I'm certainly welcome this kind of website exists, since I always thinking online library should appear long time ago. We human are slowpoke.