Questia is a new resource containing thousands of full-length ebooks. I promise you'll find many books on your topic here.
EBL is another new resource with thousands of full-length ebooks. You need to set your password on campus before you can use it off-campus.
Look in the "Online Books and (more) Primary Sources" box for links.
"Charlemagne, 742-824." (n.d.): Art Museum Image Gallery. Web. 3 Nov. 2014.