The Rats Are Coming! The Werewolves Are Here! (aka Curse of the Full Moon) by Hope Stansbury

The Mooneys are a strange family, living in a desolate section of 19th Century England. They manage to keep their secret from others and other than Malcolm, who is completely deranged and locked up in the cellar of their mansion, they look and act like a slightly strange but ordinary family. Monica, the weirdest member of the family, has an affinity for rats and jealousy for her youngest step-sister, Diana. She tries to train dozens of man-eating rats to use against Diana, while also enjoying the strapping and torturing of Malcolm at every opportunity. As the family waits for Diana's return on the night a full moon, their arguing turns to a full on werewolf brawl as they one-by-one transform and attack each other. But Diana is the one who is full of surprises . . .When sold by Amazon.com, this product will be manufactured on demand using DVD-R recordable media. Amazon.com's standard return policy will apply.