The Bare Bones: A crew of would-be documentarians film the story of a woman who believes Slender Man took her children.
Slender is not an effects heavy film, and it relies more on where you're afraid that the creature will be than on where he actually is.
The characters are shallow and unlikable, not to mention obnoxiously mundane. The middle of the film was cruel in that it grants the viewer a few rays of excited hope, only to destroy them with a sudden, unsatisfying, and all around disappointing end. (It thinks it's being deep. It's not.)