You can find better, but it's not horrible
Thirteen Ghosts is an average horror movie. It's not great but I don't agree with the main review saying that it's a huge waste of time. It's entertaining in parts, and kind of cheesy/bad in other parts. The actors try their best and I kinda liked their characters. The plot isn't hard to follow, a lot of it is typical horror movie stuff. The gore and violence here is the strongest factor as far as content goes. There are multiple images of bloody/deformed ghosts roaming around and violent attacks by the ghosts occur throughout too. The most graphic attack is when a man backs into a closing glass door and is sliced in 2. Profanity is pretty strong as well, although there really isn't any sex at all to worry about. I'd say teens 15+ can handle this just fine, but I'd suggest a lot of other better horror movies before this one.
What other families should know
Too much violence
Too much swearing