Slenderman's Shadow: Hospice takes the gameplay of Slender, and puts it in a creepy deserted Sanatorium. It features the Slenderman, and uses the same idea of having to find notes hidden around that you have to find before Slenderman drives you insane.
This is the first of Slenderman's Shadow maps, and the following Hospice map is better. Nevertheless, Slenderman's Shadow: Sanatorium is still scary, and delivers the jumps you'll recognize from the original Slender.
Slenderman's Shadow: Sanatorium is scary, but it's not quite up to the standards of the original game, and fails to add anything significant to it.