I think a lot of people missed the point of the book. To me this book was about how an atheist approaches death. Most of the characters mention that they don't believe in God and no one prays. From an atheistic perspective there is no hope for anything beyond this life, just as the characters had in reality, no hope for a life beyond the hill. So how do you go through life knowing there is no hope for an afterlife? You can:
1. Plan and keep yourself busy so you don't think about it (Jeff)
2. Joke and drink and forget about it (Erick)
3. Complain and take a negative outlook on life (Amy)
4. Live in a fantasy/daydream world (Stacy)
5. Stoically embrace the futility of action (Mathius)
Interestingly the plant only directly kills 2 of the characters... the rest are driven to it by their mental anguish, or murdered by their fellows. So, I think the book was more about how we distract ourselves from thinking about our own death, and the anguish of finally facing it head on without a belief system.