That's right, I finished this a week ago, good thing I remembered to blog.
Jonathan Strange and Mr Norrell (henceforth JSaMN) by Susanna Clarke is marketed (at least in Sweden) as "Harry Potter for adults". In my opinion this is probably not the best idea, since the books are not at all alike. JSaMN is a sort of pastiche of 19th century novels. As a Jane Austen fan I recognised the style immediately, and was charmed. The subject is magic, as in Harry Potter, but its old-fashioned style makes it a much heavier read. There are footnotes in abundance, although I would like to give new readers the advice to skip them if you find they break up your reading flow too much. They aren't strictly necessary for the story, they just add layers of depth and add to the fake realism.
Set in an alternate 19th century world, JSaMN describes the collaboration and later enmity of two magicians. There are lots and lots of different people and names to remember, and characters who are introduced in the first few chapters disappear only to be reintroduced in the last few. It is, as I said, very old-fashioned and absolutely charming. Do not read this if you've never managed to plow your way through David Copperfield and/or Tolkien. You won't make it. I know I mentioned Austen above, but that only means that the spelling and society is the same, not the style! Be warned.
I sincerely hope Clarke can follow up with a second novel to match this one. Looking forward to it.