Forger and embellisher of family genealogies. NY Times Obituary states he Developed Thriving Business in 'Mail-Order Ancestors'. A nice way of putting it.
Most of his citations are of documents are real, with bogus ones thrown in to link together families that were never actually linked together and then embellishing the connections between families especially Mayflower ancestors. ALL of his work is suspect, and anyone who quotes his genealogies, does so at their own peril of ridicule.
He may also have inserted families and ancestors in his supposed publications of source documents to support his own forgeries.
He was charging $9,000 a family genealogy back in 1890 to 1940, and doing them in three weeks or so. So many, that he made a comfortable living at it.
See article on wikipedia, or search for Gustave Anjou and forgery.