OK, the big question is whether the EPUBS are DRM-free or not. If they are DRM-free, there are a number of choices. If you want to read on your PC, but are happy being connected to the internet at the time, I recommend
Ibis Reader. If you want to read offline, Calibre is pretty great.
But if your EPUBS have ADE DRM, you are basically stuck with
Adobe Digital Editions for the Desktop. I
think the
Kobo Desktop application will also let you read ADE EPUBS, but I haven't used it myself.