Yes. That's the premise of the movie. And it's fantastic.
It looks super dumb.
And it was...in the best way possible.
Most of the violence is gory but not overly "Hostel" style gore. It's pretty realistic in the amount of blood and gross that happens.
I wasn't excited about Kristen Stewart but she did a really good job. Jesse Eisenberg plays his stoner role marvelously...it seems to be "his character type" though. (Do one thing and do it well?)
I enjoyed watching him flick between super killer and confused kid.
The small twist was kind of predictable but still worked well. There's a happily ever after (for those that worry about that kind of thing)
Basically...if you enjoyed silly movies like "Grandma's Boy" or "Waiting" you should pick this up. Don't take it seriously. It's not like that. It's stupid and fun, period.
Don't listen to the shoddy Rotten Tomato reviews. Have fun instead.