Brilliance, if it floats your boat.
The book was fantastic on its own, and the movie Fight Club simply wraps both up into a nice soapy and satirical package. If the acting, the philosophy, and the infamous ending plot twist aren't enough to get you snared into this story, then there's always the flashes of Tyler (the deranged political activist of this story) and his pornography, the very original music, and even Ikea tables to reign you back in.
Needless to say, this flick isn't for kids, unless you know them well enough. I first saw it at thirteen, and, not being easily shocked, got a grasp of the philosophy quickly enough and was able to look past the flashes of porn and the swearing and drinking and smoking and even the twisted characters to understand what was behind it.
So, if your kids are more intellectual and you don't mind them seeing things such as this and think they're mature enough to handle it, then go ahead. It all, of course, depends upon personal opinion, but this movie is rated R for a reason, is all I'm saying.
It's a thoroughly enjoyable movie, and don't let the title deceive you: this fight club is more than the usual testosterone battle that you'd expect - it's a whole world of testicular cancer, beautiful and unique snowflakes, and, of course, soap.