Good atmosphere, but it should be a bit easier to avoid Slender Man. Whenever he comes near me, it seems like the screen darkens so much that I can't see where he is or where I'm going. Maybe do something to make him a bit more visible?
In keeping with traditional Slender games, you could try making him move slower when he's being observed, and maybe make his walking animation look more scary? Random page locations would also be really good.