Today's furry fossil is Darker than You Think by Jack Williamson



Originally published as a novelette in the pulp magazine Unknown (1940), and expanded to novel length in 1948, this epic tale of a hidden race of shapeshifters (Homo lycanthropus),  the secret reason for the witch purges of the past, and considered myths in the modern enlightened world, that is awaiting the appearance of their "Black Messiah", the "Child of Night" who will lead them in their final battle with the human race.
Williamson skillfully blended '40s noir, horror/fantasy elements and a dash of pseudo-science into a refreshingly original classic that still holds up today.