The Ghost in Love, by Jonathan Carroll, is probably the most fun and fascinating magical fantasy novel I've read in a while. Cory Doctorow wrote a great review of it over on BoingBoing, which is how I found out about it, and I agree with everything he says there. There's something else that really colored the whole reading experience for me, though.
Normally when I read a fantasy or sci-fi book (or series), I expect to spend some extra time and effort in the beginning, just to get mentally situated. You have to get your bearings, figure out how this fictional world works, see what are the basic assumptions, structures, premises, etc. After that, you can coast a bit more, just absorbing the story as story.
That's not the case with this book. In terms of this particular quality, the entire book feels like a first chapter. You think you're okay once you've got the idea that a guy accidentally didn't die when he was supposed to, and then he coexists with his ghost, who can be seen by and communicate with dogs but not humans. But it just keeps going from there. You're constantly trying to figure out what's possible or not, and why on earth various things are happening. This could have been frustrating, but I found it more enthralling than anything else. It puts you in the same boat as the main characters, after all, who are also trying to figure out how their world is being rearranged. So it really sucks you in and makes you feel a part of it (similar to the way MirrorMask created such a good feeling of dreaming). I also like it just for the sheer flow of ideas. The author isn't going easy on us, or holding anything back, but just letting us drink from a fire hose of imagination. That's fun.
I'll mention one other interesting point, as long as I'm here. Carroll's writing style at times feels very simple, like very straightforward, fairy-tale storytelling. Overall, that's probably a good thing, since there's enough complexity in the content that you don't need more in the presentation. But every once in a while he'll come up with a real zinger of a line that just hits you right between the eyes, and is all the more powerful for the simplicity of its environment. Example: "Like any illness, when happiness has run its course, time is needed to recuperate from it -- sometimes an entire lifetime."
This was the first Jonathan Carroll novel I've read, but I'm thinking I should go find more. If anybody has any recommendations, let me know.