Are You Downloading Ebooks, eBooks, ebooks, or e-books?

Grammar is a topic we do here on a regular basis because I think one of the most important academic skills I can teach my son is to communicate well.  However, English being the highly adaptable language it is, it is hard to find a definitive source to settle some of the grammar questions about recent English language use.

The title gives one such example.  Many of us are getting our books in digital format, whether it is a novel to be read on the iPad, Nook, or other such electronic book device, or curriculum, resource material, or other such items.

But when we download these items, what is the proper way to refer to them?  Are they Ebooks?  eBooks? ebooks?  or e-books?

One site I've found that helps with such questions as this is Daily Writing Tips.   Not only do they debate topics like this, they have lots of resources on the subject, including a section on Grammar 101 and a basic grammar (their choice is) eBook (although they suggest that the most popular choice is probably e-book).  If you subscribe to their blog, you will get a daily email relating to writing, which can be helpful to students, teachers, and bloggers alike.