"Regress!" You shout the command word for the age reversal spell, and picture yourself twenty years younger. You feel quite silly attempting to 'cast a spell' but you could use a good laugh.
Then, you hear a poof sound as a cloud of smoke appears all around you. Coughing, you wave the smoke out of your way, and walk out of the cloud.
"Who booby traps a book!?" You shout out loud, not sure that this is some type of joke. Someone probably stood by you all night whispering the words the girl spoke to you in the dream, and then set the book down, and naturally, you pick up the book and set off the trap. It was an elaborate prank one of your friends must have pulled over you.
"Well, I'll just have to find out who and get revenge...." You suddenly stop, noticing a couple of things. The first being that your voice is much higher pitched than it used to be. The second is that the smoke is clearing out of your room, and your room looks a lot bigger. The last, is that your clothes are several sizes to big, and about to fall off.
"It.... Worked?" You mutter, in disbelief, trying to comprehend the change that occurred. Keeping a good hold on your pants to keep them up, you stumble out of you room, and to the bathroom to look in the mirror. Staring back at you is not your adult self you expect to see, but instead a five year old boy.
"The book.... Really worked...."
You stumble back to your room, being careful to keep your clothes on, and open the book back again. The spell worked, meaning that the other spells in the book should also work.
Time travel, ageing forward, changing other people's age, freezing time.
You could potentially cast any of these at any time if you kept the book on you. Still, the books mention energy cost to each of the spells. Perhaps, you may become fatigued if you try casting to many spells in a row.
"What do I do now?" You wonder.