The new guide works by searching genealogy research on FamilySearch that has already been conducted on your Virginia ancestors. You select the county and then an extensive list of books and articles appears. Some of these are scanned books available on FamilySearch.org while others could be available most anyplace on the Internet, such as on American Ancestors, Google Books, and Internet Archive. The books may focused on all the residents of a particular county or, in some cases, on only one family.
You can’t trust every word of published family histories, but they generally help you save a lot of time and hard work. They may contain photographs, old letters, and family documents that you normally do not encounter in typical family history searches. Well-sourced family histories can help you quickly trace your family back several generations.
You can learn more in an article by Nathan W. Murphy in the FamilySearch blog at https://familysearch.org/blog/en/studied-virginia-genealogy/.