I just read through the FAQ of U.S Copyright yadda yadda and it doesn't say crap about ebooks. Do they protect ebooks, or what?
Salamander mentions that you have other posts, but I haven't read them. I just wanted to say that the copyright is for the manuscript that you submit to them. The copyright is then good for ebook or print. I've been writing non-fiction and fiction for decades and I always copyright since it helped me in a court case. The online submission is an easy step by step process.