I don't know why this never occurred to me. Reading on my phone strains my eyes with the bright screen and small display (not to mention very limited battery life) but I think Kindle and Kobo are overpriced (I just need something that can read PDF and EPUB files!). I even thought of assembling my own e-book reader with a battery-powered Raspberry Pi. Somehow I didn't even realise there are commercial Android-based e-book readers. Thanks a lot!