Yes, a revenge flick, my most favorite meta-genre, but good enough to be better than most. What I like best about this movie is the format in which it's told. Here's the high level overview, copied and pasted directly from Wikipedia.org...
"...the movie tells the story of four documentarians who journey deep into the jungle to film indigenous tribes. Two months later, after they fail to return, famous anthropologist Harold Monroe travels on a rescue mission to find the group. Eventually, he recovers and views their lost cans of film, which reveal the missing filmmakers' fate."
(Their fate is pretty obvious, btw.) In any case, the format gave it a true sense of reality as all you know about the four filmmakers is what you see as you watch the films with Mr. Monroe, the anthropologist.
It's a fascinating film, but heed the warnings! It really is as graphic and disturbing as they say and there are scenes of actual animal death. Also, I highly recommend reading the rest of the Wikipedia article. This movie knocked people off their asses back in the day!