The game feels pretty laborious. It was fun(ish) for the first minute, but the more pages you got the more it turned from a "survival horror" to a stop, start, stop, start game. If it wasn't for the achievements and the high-score board, well... this would be a really boring game.
The fact that you can only go left or right almost completely removes what made the first Slender 3D game scary - You could go all over the place and, sooner or later, he'd show up, but you wouldn't know where. And if you did see him in the distance, it did give you a slight chill. On this, there's only two guaranteed places he can come from - left or right. It'd be cool if he all of the sudden appeared a little off to the right behind a tree when the flashlight goes over it, and that'd make this game a little less predictable... but it really didn't scare.
The first time I saw slender, okay, it was a bit of a "ooooh" moment, but when I found out all he did was just linger around you and not move a single muscle (No black tentacles sprouting from his body either), he really just became a nuisance. You should've made him far more threatening and less predictable, and when it does come to getting a game over, you should've added some typical Slender-style flash/static/crackle shots before ending, not just going STRAIGHT TO THE HIGH SCORE BOARD.
The stamina system in it is ridiculous. How quickly it drains from the pace you walk at is pathetic, really. Like I said earlier, it turns into a repetitive stop-start-stop-start game which provides no fun or thrills.
I think you need to do a lot of work on this, or just start from scratch to create a completely different style of game. I do appreciate the effort that went into this, but it felt very lackluster.
