You open it up to a random page… It’s extremely blurry, you quickly close it. You are in fact, dreaming. It’s a good thing you didn’t open that door.
Your dream journal serves as a constant anchor, if it’s blurry it means you cannot know what’s in it as that information is blocked out from your sleep self. If you continue to look at the book until the words become clear your brain will consider the realm you’re currently in to be the “real world” and you will be locked into it unless proven otherwise.
The knocks continue.