Essentially a rip off of "The Exorcism of Emily Rose" told through the prism of the extremely tired "found footage" genre. The gimmick in this instance is that the overtly theatrical and self-important preacher conducting the exorcisms openly admits to fraudery on his part, even a complete loss of faith, and is seeking to demonstrate (care of the film crew that follow him on this, his supposed last exorcism of the title) how all the possessions he encounters are products of obsessive religion, skewed psychology and mental disorders. By using bed shaking, demon howling, crucifix smoking trickery he gives the families of the "victim" exactly what they want to see and hear to clear the way to uncover the real root of the problem. The actual morality of that process is quite messed up in itself - in reality it would be feeding a potentially dangerous mindset with more dangerous material, but reality takes a significant backseat as the film progresses. Although the majority of the film is interesting in its attempts to debunk the notion of possession and exorcism the performances never feel true enough, or the script real enough, to effectively sell the notion of the documentary style - as much as the film tries to seem real it always ends up feeling scripted, and is frequently more silly than scary.
Logic flies out of the window in the final part of the film -
the girl has quite convincingly been revealed to be mentally unstable rather than possessed and the three protagonists have been threatened not only openly by a shotgun wielding father, crazy with religious fervour, but suggestively in drawings by the girl - variously chopped to bits and burned to death. At which point you'd probably think it was time to leave or call in the police. Instead the trio march promptly to their predicted deaths but only because of the stupidity and selfishness of the preacher; all the interesting ambiguity of the possession is dispensed with as he confronts a lamentably inconsistent (not to mention poorly executed) special effect - a demonic and sentient fire, recorded on camera for all to see - which he attempts to confront, along with a baying mass of crazed Satanists, having belatedly rediscovered his faith. I guess seeing a fire demon might do that.
We are left with same image of a camera crashing to the ground which ended "The Blair Witch Project" so effectively a decade ago but without any of that original surprise - which sort of sums up the sub-genre it has unfortunately engendered.
One final thought - if this film really was meant to be "found footage" who edited the material into the final film? And why on earth would they add "creepy" horror music to the soundtrack? This is basically horror film-making by committee without an original premise or the sense to follow an idea through, and because it was cheap to make and went down well with the late night popcorn crowd it even spawned a sequel. I won't bother with that, and I wouldn't recommend you bother with this.