I'm developing an Epub reader on BlackBerry java platform, and I'd like to know if there is a possible way to register my application as the default reader for Epub files, like if a clicked on an attached Epub file within an email, or a link to that file in browser, or even if I clicked on it while browsing all files locally, am I going so far with this? is it possible?
Try using the Content Handler APIs, which allow you to register an app to handle files of a particular extension and content type (e.g. .epub and type application/epub+zip).
See this BlackBerry reference document for more information
If you install the full SDK, you should also find the CHAPIdemo sample code under samples/com/rim/samples/device/chapidemo.