Brennan

“This much I'm certain of: it doesn't happen immediately. You'll finish [the book] and that will be that, until a moment will come, maybe in a month, maybe a year, maybe even several years. You'll be sick or feeling troubled or deeply in love or quietly uncertain or even content for the first time in your life. It won't matter. Out of the blue, beyond any cause you can trace, you'll suddenly realize things are not how you perceived them to be at all. For some reason, you will no longer be the person you believed you once were. You'll detect slow and subtle shifts going on all around you, more importantly shifts in you. Worse, you'll realize it's always been shifting, like a shimmer of sorts, a vast shimmer, only dark like a room. But you won't understand why or how. You'll have forgotten what granted you this awareness in the first place

...

You might try then, as I did, to find a sky so full of stars it will blind you again. Only no sky can blind you now. Even with all that iridescent magic up there, your eye will no longer linger on the light, it will no longer trace constellations. You'll care only about the darkness and you'll watch it for hours, for days, maybe even for years, trying in vain to believe you're some kind of indispensable, universe-appointed sentinel, as if just by looking you could actually keep it all at bay. It will get so bad you'll be afraid to look away, you'll be afraid to sleep.

Then no matter where you are, in a crowded restaurant or on some desolate street or even in the comforts of your own home, you'll watch yourself dismantle every assurance you ever lived by. You'll stand aside as a great complexity intrudes, tearing apart, piece by piece, all of your carefully conceived denials, whether deliberate or unconscious. And then for better or worse you'll turn, unable to resist, though try to resist you still will, fighting with everything you've got not to face the thing you most dread, what is now, what will be, what has always come before, the creature you truly are, the creature we all are, buried in the nameless black of a name.

And then the nightmares will begin.”
― Mark Z. Danielewski, House of Leaves