Useful for any game that features the supernatural. Easy and simple system. A consistently focused product.
Consistent focus leads to overly repetitive themes in campaign material and rules.
But, you can burn through the ideas in the book after a few adventures. I heard a lot about Unknown Armies last year and all of it was good. I saw the authors and figured that between those names and the good press I would give it a go. So, I got the book and sat on it for about a year, digging through other things. Then I picked it up and read it.