Originally Posted by duokan.com

Duokan(meaning “read more”） is an alternative system for Kindle 3 developed by a Chinese team. It's also available on Kindle2/Kindle DX/Kindle DX Graphite. It's free for non-commercial use.

It doesn't overwrite the official system in Kindle, but worked as a secondary system. After installation, there'll be a system selection menu shown when Kindle is restarting. You can select from Duokan system and the official system by pressing "Q" and "W".

Duokan improved the compatiblity with Chinese characters of K3，along with some other key features. It supports Text、ePub、PDF、mobi、CHM、Zip、DOC、djvu ；it has a new PDF reader which provides full-screen reading，cropping the white margin and better support of two/four-column papers.

Duokan can also use the "partly-refresh" method to make the refresh faster when switching pages （a popular function for E-ink readers in China），instead of a full-blacked refresh in the original system.

For me（I'm a Chinese)，Duokan works better in comics and some complicated PDF files.