Stine made a mint with the "monster" sphere -- along with the aforementioned Monster Blood and Curse of the Mummy's Tomb, he penned The Girl Who Cried Monster, Egg Monsters From Mars, How to Kill a Monster, The Werewolf of Fever Swamp, The Abominable Snowman of Pasadena, The Blob That Ate Everyone, The Beast From the East, Vampire Breath, and Werewolf Skin.
That last one brings us to another key grouping: body parts. This cluster includes Werewolf Skin, Monster Blood, The Headless Ghost, My Hairiest Adventure, and How I Got My Shrunken Head. As you can see, it also presents us with our first tri-circle diagram.
Overlap: Monster Blood