FBReader, the Open Source multi-format e-book reader, is being ported to Java (the original is written in C++). See
FBReader for Google Android (and other Java platforms). This isn't available for download yet, but it means that there will be at least one world class e-book reader for Google Android smartphones.
Note that FBReader and FBReaderJ do not currently support any e-books with DRM. However, this may change in the future see
Contribution Guidelenes.