You probably know of Bluefire Reader on iOS, but unless you’ve been following this blog you might not know that Bluefire have been working on an Android version of the app since last year. BTW, they already released an Android app which had been built for one of their customers, Libri.de.
Bluefire Reader is a wildly popular iOS app that supports Epub and PDF. Unlike Stanze, Bluefire reader supports Adobe DE DRM. It works with any number of ebookstores and it even supports library ebooks. It has long since replaced Stanza as the touchstone reading app for iOS, and I would say that Bluefire Reader might give Aldiko, the leading Android reading app, a run for its money.