The blob that ate everyone - R. L. Stine

They're baa-ack! Make way for the bestselling children's series of
all time! With a fresh new look, GOOSEBUMPS is set to scare a whole
new generation of kids. So reader beware--you're in for a scare!
Read it and scream!
A famous horror writer. That's what Zack 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 Zack 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 Zack writes is starting
to come true. . .