Digital Editions on Mac crashes after adding a book

I am running Digital Editions 2.01 on a Mac with El Capitan OSX. After adding a possibly malformed epub Digital Editions crashes every time I try to start it. Is ther something I can do to reset the software. Do I need to remove all books from the Digital Editions folder? Is there a hidden Preference I need to delete? Or a datbase somewhere? I was adding the book to check it since it wouldn't display on my e-reader.

--MH