Android ePub reader

We have a project on both Android: What we are looking for is quite a simple epub reader that would allow teachers ito download teaching handbooks and resources to read - normally without paying a fee, so we don't want a complex itunes paid-for store model. Ideally they would be able to download epub files from our own server and keep a bookshelf on the phone of training manuals they can refer to. I wonder if you can give me a quote on this Android app. How long it takes you to finish the work? Thanks