Ever use Deja Vu format by Lizard Tech? Maybe you did in another timeloop.
Here, download this file to test it out, and the DejaView plugin too.
I think .djvu files are superior in quality and compression to PDF but the GUI is less mature, editors are expensive, and trying to make djvu files for free requires tracking down and rigging together different outdated apps. I use .djvu only for big scanned documents that have complicated layout with pics, equations, and text. Most of the .djvu files you find on p2p networks are textbooks and technical manuals.
In the beginning most of the files listed were in djvu format, but it was a greater pain downloading and using the less functional LizardTech viewers than the more bloated but better featured and more universal Acrobat. Good news is that there is an alternative to Acrobat: Foxit Reader - smaller and quicker app. Also, the primary thing that makes Acrobat retarded is its hefty set of nearly useless plugins that load everytime you start Acrobat. Disabling these speeds up Acrobat quite a bit. Go here for instructions on how to do this.
Acquiring fringe knowledge is like digging for diamonds in a mine field.