Currently, I'm using Sumatra PDF to read EPUBs on my Windows desktop. Unfortunately, it doesn't allow copying text to my clipboard.
What's a good EPUB reader that allows my to copy interesting passages to copy them into Evernote?
I would like to recommend calibre, an open source ebook reader. It is able to read .epub files and is available for Windows. It also has copy support where you should be able to copy text found within passages.
calibre is an e-book manager. It can view, convert, edit and catalog e-books in all of the major e-book formats. It can also talk to e-book reader devices. It can go out to the internet and fetch metadata for your books. It can download newspapers and convert them into e-books for convenient reading. It is cross-platform, running on Linux, Windows and OS X.