This is an excellent novel ... like the best novel, it not only gives you wonderful characters, but uses them to hold the magnifying glass up to your own life as well. The book has several ominous and fascinating implications for our own lives.
It centers on a mythology that features Travelers - humans throughout history with the ability to escape this dimensional plane and gain spiritual knowledge - and Harlequins, the warriors who guard them. The most interesting part to me was the simlarities between Travelers and the Baha'i concept of Progressive Revelation.
Needless to say, on the other side of things there's a vast conspiracy of evil folks using the new technology of our society to create a virtual Panopticon. For those of you unfamiliar with this appaling conceit, Jeremy Bentham created the Panopticon - a prison in which prisoners constantly feel as if they're being watched, even if they're not. So they automatically behave better and modify their thinking to the status quo. Twelve Hawks posites that this is invisibly being done to us on a global scale right now.
For me, it's not as if I've never thought of these concepts before, but he ties them all together into a single description of a society that's evil in its subtlety, making an idea that's hard to ignore. The characters here are well-drawn and the plot moves quickly, too. Highly recommended.