The blob that ate everyone (Goosebumps) by R L Stine - old paperback
A famous horror writer. That's what Zackie Beauchamp wants to be. He's writing a story about a giant blob monster. A pink slimy creature who eats up an entire town! Then Zackie finds the typewriter. In a burned-down antiques store. He takes it home and starts typing. But there's something really odd about that typewriter. Something really dangerous. Because now every word Zackie writes is starting to come true. .