Disruptive Conversations

Anyone else wondering when we will all standardize on what we call an electronic book?  I routinely see some or all of:

• e-book
• e-Book
• eBook
• ebook
• Ebook

I haven't personally seen "EBook", but I could imagine that being a candidate, too.  What do you all think?  Which one should we use?

P.S. Of course, some 30-ish years in, we still don't know whether it's "e-mail" or "email" :-)