Re: Nature's Nobility
It doesn't matter to my point what the book contains. My point was that at the time Lucius embraced Severus he had a reason to think Severus was not pureblood because of his last name. Whether he could have obtained that knowledge specifically from Nature's Nobility or some other source is unimportant. We know from Albus' description of Tom's pastime in his first 4 or 5 years at Hogwarts that there are wizarding genealogies. (Since the full title of Nature's Nobility describes it as a genealogy I used it as an example but it is not material.)