Not bad. Not bad at all.
Slender makes it up with its chilly atmosphere. It touches on what most humans fear-the unknown(this is just my assumption). I'm easily scared when it comes to the horror genre(be it movies or games) and if you are the same you might want to try this one out. Or not.
Slender isn't something great. It does get old after a while though but for an indie it generally set aside the fancy graphics and immersive gameplay that you can find in most horror games and focuses on the basic aspect of generating the emotion we called fear that most horror games try to generate.
I'm done with the game. Invited my siblings to play the game. Their distorted scared face seen even for mere seconds.