Grave Peril is, really, where the Dresden Files started to find their footing.
This isn't to say the previous volumes were bad but much of the series' trademarks start appearing here. We get the introduction to a number of important characters, the layout for the series' overarching plot, the beginning of a major plotline which will occupy the books for many volumes, and plenty of information on the series' mythology. There are also several shake-ups with the existing cast and status quo.
The premise of Grave Peril is Harry Dresden and his longtime associate, Michael Carpenter, successfully hunt down a ghost before becoming involved in a plot involving a much-more powerful creature stalking a young seer. They receive help from a White Court vampire, basically an incubus, named Thomas who is unusually friendly to the duo. Harry's on-again, off-again girlfriend Susan Rodriguez also comes to the town. This, before all of the above converge at a party thrown by a group of murderous vampires out to destroy Harry.
If this sounds like a convoluted plot, it is. This is not a book with a single coherent narrative but multiple ones which all reach a climax. This is both a strength and weakness of the book because it's hard to keep track of everything which is going on. Later books would have a stronger central narrative while not sacrificing the mystery which is inherent to the series' appeal. While everything does tie together, it does so in such a loose manner that I doubt Jim Butcher would have done this book the same way if he'd had the chance to rewrite it.
The real appeal is that it move Harry Dresden away from the "case of the week" format which, while appealing, was nothing really special in the Urban Fantasy genre. After this point, there's a central guiding narrative which, while mysterious, drives the plot forward. The Red Court, previously just a background element of the series, moves to prominence as enemies of the White Council and Harry in particular.
The new characters introduced in this book are also ones which start fleshing out Harry's world. Michael Carpenter, the Knight of the Cross, is a rare case of a positive Christian warrior in urban fantasy fiction. The majority of individuals with strong religious convictions are often depicted as fanatics or lunatics in these sorts of books, so it's nice to have one who is motivated by his faith to do good.
The fact Harry remains agnostic or, at least, irreligious means the two of them have some interesting conversations while maintaining a level of respect. Thomas the "Good" Incubus is a character who doesn't get fleshed out too much here but the very fact he's helping monster hunters for, seemingly, benevolent reasons makes the world more complex. If monsters can be good people then the world has gotten a lot more grey.
I also loved the characters of Charity Carpenter, Lea, and Susan Rodriguez in this book. The previous bookw had a heavy noir tone which restricted women to somewhat questionable gender roles despite the subversion from Murphy. Introducing a larger and more varied role for women in the books (as well as making the central villain here one) helps make this a better book overall. Later fans of the series may note that a lot of the series' future plot twists are set up here and fans will often find themselves re-reading this one for clues.
There's a lot of hilarious moments in this book like Harry Dresden going as a cheap Dracula knock-off to a vampire Halloween party, Lea's attempts to "protect" Harry by turning him into a dog, and poor Harry realizing that it is NOT wise to bait a dragon. The drama is strong, too, with several events happening which change the status quo forever. Bianca and Kravos aren't very well fleshed-out villains but serve their purpose amiably in the story.
In conclusion, Grave Peril is the first really good Dresden Files book. I am tempted to encourage fans to start there if they really want to get a sense of what the book is leading up to. This is where the series began and it only gets better from here.
9/10
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