Really, Die is just a less elaborate Saw: the mastermind Jacob kidnaps suicidal people and puts them through a series of death tests. Those who live are supposed to be reborn, cherishing their life anew and forming a cult-like group (as happens with some of Jigsaw's victims in the later Saw movies). Like Jigsaw, Jacob physically marks his victims, burning a die roll into their flesh.
But where Die differentiates itself is in its simplicity. Instead of the insanely complicated traps that Jigsaw constructed, Jacob prefers to have his victims confront their means of attempted suicide: drowning, drug overdose, Russian roulette, etc. This small bit of realism grounds the film and makes it feel much less forced. Admittedly, the likelihood of a person having the ways and means to kidnap and torture 6 people simultaneously is pretty slim, but Die gets as close as it's going to get.
While disappointing when compared to the original Saw, Die seems to be a more fitting sequel than the later Saw films. Its focus on characters and its restraint in elaborate torture techniques allow the film to avoid the popular torture porn sub-genre, making it more watchable and more effective.