I keep wondering if Henry is going to write into the book and these portal doors are going to appear different places and bunch of evil people are going to escape into the real world.
Could be. Henry being the author gives him a lot of power, potentially as much, even arguably more than the sorcerer and apprentice. All he would do is write something into existence, and out it pops.
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"That’s how you know you’ve really got a home. When you leave it, there’s this feeling that you can’t shake. You just miss it." Neal Cassidy