So, yes, I am finally starting this series after looking at it on my selves for a couple years (I actually have the old covers). The think that stood out the most to me was the world itself. It is so incredibly well developed. While it is based on our modern-world, the "dark areas" are taking over. Now these are some pretty seriously scary places that I would never want to visit. They were just so well written that I got chills any time someone had to go there.
The fae creatures themselves, both Seelie and Unseelie, were also very well developed. I loved the scenes of Mac running into the Seelie prince. They were humorous and a little frightening at the same time - it takes skill to write that mix well. The various lesser "baddies" that Mac runs into were also given plenty of details - Moning didn't skimp on them just because they may not have been as important. They were a vital part in setting the stage and atmosphere.
The story is a bit unpredictable - but it's in a good way. I was constantly wonder what was going to happen next and then I was surprised to find out what it was. There is plenty of action and a bit of sleuthing and detective work that really drew me in. I needed to know "who-dun-it". There is a bit of resolution at the end, but not nearly enough to satisfy me. I'm really glad I have more of the series ready to pick up as soon as I can.