"I'll to my book,
For yet ere supper-time must I perform
Much business appertaining...."
See in text (Act III - Scene I)
Pleased with how Miranda and Ferdinand have taken to one another, Prospero states here that he must continue consulting his book in order to carry on his plans. His books have been established as magical already, but the way this scene has portrayed Prospero as a playwright further suggests another sign of the metadrama, or play within the play: Prospero is not only consulting his book for a spell, but he is looking at what will happen in the next scenes of the play, providing an enticing bit of tension as to what will happen next.