Unfortunately, ADE does not support complex languages with diacritics such as Kannada. (Diacritics are treated like separate letters and are displayed next to the base letter.)
This means that most existing commercial ADE compatible (hardware) eBook readers that haven't been adapted for the Indian market won't be able to display your ePub correctly.
This leaves only Webkit based ePub reader apps, for example, iBooks and Bluefire Reader. I also tested your ePub with the Kindle KF8 Previewer
app and it seems to display your book correctly in Kindle Fire mode after I added the correct language information metadata to the ePub.
I.e. as of now, your best bets are iPhones, iPads, Android devices with Webkit-based reader apps and possibly the Kindle Fire (after ePub-to-KF8 conversion).