The three applications noted previously, Overdrive, Freda and Book Bazaar are the three I have currently kept loaded. The rest of the ones I tried, I junked. I vaguely favor Overdrive, but not by much.
That said, I tend to drop to the desktop and use either fbreader or Cool Reader instead. There isn't currently a real winner, IMO. Good luck.
I don't know if any of those yet support ePub3. I'm not sure I've run across an ePub3 in the wild.