You really need to see this! Never mind the knee-jerk recommendation from boring old Quentin Tarantino, this truly is a unique movie. Director Jack Hill said that its theme was unconditional love, and he succeeds magnificently in selling the idea of people who ought to be genuinely evil to the max, but aren't because they can't help it, and are guarded by a protector who isn't evil either, but will literally give everything for them. Of all the deranged kidult movies, this is definitely the best. Lon Chaney Jr., never a truly good actor and an almost unemployable dying alcoholic when he made this, liked the script so much that he managed to stay on the wagon throughout and gave one of his best performances ever. He even sings! (Apparently many retakes were required - the song genuinely has to be heard to be believed.)
The complete stupidity and uselessness of the hero and heroine are way ahead of their time, as is the notion that the supposed monsters genuinely can't help it. And don't worry about finding the title character disturbingly sexy - she's much older than she looks. Right from the beginning, when horribly typecast Mantan Moreland's cameo ends in the worst possible proof that for once he's absolutely right not to want to go anywhere near that creepy old house on the hill, you know this film's going to mess with your expectations. It was so nuts that it was almost impossible to sell, and had to be re-titled "Cannibal Orgy" (not strictly accurate), and then, when that didn't work, "The Liver Eaters" (even less accurate). But seriously, how could you have a better title for anything than "Spider Baby"?