Where do i get free Ebooks that is compatible with pandigital multimedia novel from android?

i bought this new multimedia tablet with color ereader and i have barnes and nobles but they only have 4 free books and my dad says for now search for free e books but so far i searched borderbooks and the main library and it's incompatible and the file won't open and some programs and downloads such as adobe flash player is incompatible for my device any ideas?