O livro que você está procurando pode ser Dragon Fall, por Lee J Hindle. Escrito em 1984. Adorei este livro quando era criança.
da contracapa:
It started late one Saturday night after he got home from a rock concert. Something grabbed him from behind. Something that wanted to hurt him.
Then the voices began. Threatening. Warning. Vicious.
At first he thought it was his imagination. Gabe had an excellent imagination. He used it to design monsters. Five-foot-tall, red-eyed, jagged-toothed monsters. The kind that sold to toy stores for big money.
But Gabe isn't thinking about money right now. Because a night alone is turning into a night of terror. He is looking at the worst nightmare his mind ever imagined. And they're coming to tear his flesh.
Now... Right now!