Most Familienbücher contain information compiled from original sources- typically church records, vital records, and sometimes other sources. They're locality based. They contain information on individuals in a given locality for a specified term of years. Familienbücher are usually arranged by family, with lists of nuclear families and their members, along with their birth, marriage, and death dates. Because they're compiled records, they don't contain all the information contained in the original sources. For example, they may not contain the names of baptismal sponsors, or marriage witnesses, or notations about consanguinity, which are usually important clues that are found in the original church records. Because they're copied from other sources, they also inevitably contain inaccuracies.
Familienbuch der Pfarrei Mettendorf: Dekanat Neuerburg 1641-1900 (Family lineage book for the parish of Mettendorf, deanery of Neuerburg) is available at the Family History Library in Salt Lake City (http://www.familysearch.org/eng/Library/FHLC/frameset_fhlc.a...
search for Place = Mettendorf), but has not been microfilmed, so it can't be obtained at local Family History Centers. To purchase a copy, check with the publisher: the Westdeutsche Gesellschaft für Familienkunde (West German Society for Family Study):http://www.genealogienetz.de/vereine/wgff/publikationen5.htm
Or you could check the original church records for Mettendorf. They've been microfilmed by the Family History Library and can be rented and viewed at any Family History Center.
In the future, please be aware that online German>English translators are pretty bad, as you can see by comparing the translations I provided above with those in your original post.