I watched the final of series two last night. Really good show. Pity they cancelled it, the ending (i.e. setup for series three) looked really interesting.
That said, some really nasty stuff happens and I wouldn't recommend it to anyone easily disturbed by, for example, sexual violence or dismemberment. However, if you're prepared to handle some violent and freaky stuff, it's well worth it.
The way the magic is portrayed is really neat, reminiscent of Tim Powers novels to me. It feels like it has a logic to it, but it's not a very nice logic in most cases. The acting is universally good and the scriptwriting too. The characters are interesting and are forced to deal with situations that have no good way out, which makes some powerful scenes.
The direction tends to include a lot of dark scenes where you can't see what's going on, but aside from that there's little to complain about.
Why does it seem like every TV show this good gets cancelled?