Wikipedia
FBReader
FBReader is a free and open source e-book reader for Linux, Microsoft Windows, Android, and other platforms that is free of page-view tracking and other invasions of privacy.
It was originally written for the Sharp Zaurus and currently runs on many other mobile devices, like the Nokia Internet Tablets, as well as desktop computers. A preview of FBReaderJ (the Java port) for Google Android was released on April 13, 2008.
Supported formats include EPUB, FictionBook, HTML, plucker, PalmDoc, zTxt, TCR, CHM, RTF, OEB, mobi without DRM, and plain-text.