Texts from ePUB ebooks can be exported and saved as separate documents which can be then edited using a text editor or word processing tool.
For example, you can use Calibre e-books management software for Windows, Mac and Linux to convert .epub e-books to Word documents (.doc, .docx.). But sadly Calibre can only export to HTMLZ.
Once you have it, rename .htmlz file extension to .zip, unpack the .zip archive and import index.html file to Microsoft Word.
On OS X you can use Pages, because it supports ePUB format in the latest version.
Updated: August 2, 2016