On Monday, 22 March, we had a class at the library on finding genealogy books online. The class concentrated mostly on full text books, ones that you can download to your computer or simply read online.
The State Library of North Carolina has a digital repository that fits into that class. It from the home page (http://digital.ncdcr.gov/cdm4/index.php), click on "View Collections" or go directly into a search.
The collection deals mostly with North Carolina, of course, but there are other references there as well.