Didn't know that this is the final installment of Rob Zombie's Firefly trilogy, following House of 1000 Corpses 2003 and The Devil's Rejects 2005. Now, having watched this film, may check out the prequels just to find out the back stories of the three psychopathic killers.
Note: Per Wiki, Inspired by 1970s horror films such as The Texas Chain Saw Massacre (1974) and The Hills Have Eyes (1977.) If you remotely like this kind of horror genre, don't miss The Hills Have Eyes that is one of the best gory horror film and more importantly based on plausible premise. Consider to be warned and prepared for what to expect during the early scenes but still shocking to experience the rest.