I finished the fourth book in The Dresden Files, Summer Knight, while in Hawaii. It is very good but it doesn't have the knockout punch of Grave Peril. What I noticed is a sense of maturity in the series; there are several elements from previous books that make their way into the story. Plus, Jim Butcher's writing style is growing on me.
The plot involves a war between the faerie courts that Harry gets involved with. He'd rather not be anywhere near dueling fae but there's a little matter with the wizard vampire war that he started in the last book. If he doesn't make nice with the Winter Queen he will be found guilty by the White Council and given over to the Red Court as a peace offering. Quick note: peace offerings to vampires work wonderfully unless you're the offering. Another quick note: this all makes perfect sense if you've read the first three novels.
Butcher's best decision with this work is to reveal more of the continuing characters he's developed. That is the key to the survival of any series. They cannot become a rehash of the same story told again and again. (BTW, that's exactly what happened to Star Trek and James Bond, which is why both franchises are getting restarted.) In this book, we find out about Harry's first love, his first mentor, his current love, and some kids he helped a couple of books ago. All of this brings the reader in for a satisfying journey.
Three stars for Summer Knight.