I love a good fantasy book, particularly ones with interesting characters, a good dose of realism, and a solid system for magic.
I love it even more when that fantasy element gets blended with contemporary of science fiction settings, so that you can really develop ideas and run with them. But, in the vast majority of books that attempted to take fantasy out of the middle ages, I was always a bit disappointed.
Why? Because you'd have, say, modern witches and wizards and heroes using swords. I mean, who takes a sword to a gun fight?
At this point, I must point out Brent Weeks' Lightbringer series. He did an amazing job of having full epic-fantasy in line with a world that was of a similar technological age to the 1700s. I'm sure there are other authors who have done a similar job, but as yet, I've not read them.
What this has meant for me as a reader is there has always been a hole, a missing tooth, where you could seamlessly blend modern or futuristic tech with magic and fantasy. That hole has been nagging away at me for years, but it's only been recently that I've had the skill or knowledge to do something about it.
Hence, The Magic Circle.