I am trying to develop an application that reads e-books in EPUB format. I'm a beginner, so I don't know from where I should start from to develop it. Could anybody help?
You may find the IMP eBook reader is one app developed for this precise purpose. It is available for download at http://droidimpreader.codeplex.com/ , and you may access its source code at http://droidimpreader.codeplex.com/SourceControl/list/changesets .
Another option is the FBReaderJ, whose source code is available at http://www.fbreader.org/FBReaderJ.
Finally, you might want to check out daisy-epub (http://code.google.com/p/android-daisy-epub-reader/). Its source code is available for download at http://code.google.com/p/android-daisy-epub-reader/source/checkout .