I shall put this under a cut because it's very hard to say anything at all about this book without giving out huge spoilers for the last one in the series.
So, at the end of Changes, Harry Dresden is shot by an unknown assassin and falls into Lake Michigan. At the beginning of this one, his spirit is sent back to Chicago to help his friends and discover who killed him.
If this were a television show, this book would be the flashback episode. Which is appropriate, since Harry returns in a form that consists, as he's repeatedly told, only of memories. As such its rather slower, plotwise, than Changes, but that's not a bad thing - the last book was a frenetic rollercoaster and this one gives the reader and Harry a chance to reflect on what happened and the consequences of that.
It was also interesting to see Harry dealing with problems when he couldn't take his usual brute force approach and had to think things through rather more thoroughly than usual. Once again I'm loving the way that Butcher picks up things from previous books and uses them in unexpected ways later on - while the involvement of one character in the denouement seemed reasonably obvious from the outset, there was a second who I'd never suspected was taking part in things.
And while this book doesn't end on quite the cliffhanger that the last one did, it still leaves the reader eager for the next one. Excellent stuff.