I also use and highly recommend Moon+ Reader for Android. It has a great number of features, supports a multitude of filetypes, and is still simple to use.
I use Calibre on PC and have just recently started using the BookFusion extension and app which syncs my books and reading progress between my phone and computer. The BookFusion app isn't the best mobile ebook reader I've ever seen, but is good enough to recommend if you want to use the syncing feature.