Time for another confession: I am unfairly prejudiced against werewolves. Maybe it's because I have an irrational fear of dogs, or maybe it's just the whole icky shapeshifting aspect, but I've never liked werewolf-oriented fantasy. When my favourite supernatural series has a book or episode featuring werewolves, I just don't enjoy it as much. For that reason alone, while my re-reading of Storm Front persuaded me to give it a fourth star, I was biased against Fool Moon from the start. If, on the other hand, you like werewolves, you might be predisposed the other way.
But my disclaimer digresses! Werewolf plot elements aside, Fool Moon seems to have less magic and exposition about the magical world of the Dresdenverse that I find so appealing. Aside from a couple of potions, a demon summoning, and a whole lot of combat evocation, Harry doesn't perform much magic, and we don't learn anything more about the White Council, the Nevernever, etc. While this book introduces the Alphas and changes the dynamic between Harry and Murphy (again), it's one of the most stand-alone novels in the Dresden Files. Hence why one's enjoyment rests so much on one's disposition toward werewolves.
When I first read the series, I didn't pay much attention to Harry and Susan's relationship, mostly because I was strictly a Team Murphy kind of guy. Yet the entire reason I'm re-reading the Dresden Files series is in preparation for reading Changes, in which Harry and Susan's relationship plays a major role. Furthermore, by neglecting this part of Harry's life, I've neglected a major part of his character.
Harry's reliance on Susan testifies to the veracity of their bond and his feelings for her. Harry allows himself to be vulnerable around Susan. This runs counter to his code of chauvinistic chivalry, and it may be a byproduct of necessity rather than design—but we all need to be vulnerable at times; we all need someone on whom we can rely.
This theme echoes throughout the book. Carmichael, Murphy's partner, dies while defending Murphy from the loup-garou loose in the precinct. Of course, Carmichael is the resident Dresden-doubter at SI, so we're not supposed to like him, no matter how much Harry goes on about him being a "decent guy." It's clear from Murphy's reaction, however, that she was close to Carmichael—professionally—and his loss is all the more significant for that reason. The Alphas rely first on Tera and then on Harry; MacFinn also relies on Tera. In this light, Harry's lack of trust in Murphy at the end of the book seems particularly unfortunate, especially after the events in Storm Front damaged their friendship. Harry feels responsible for Kim Delaney's death, because he denied her knowledge that might have saved her life, believing it was protecting her from retribution from the White Council. Now Kim is dead, forcing Harry to reexamine how much he withholds from Murphy. Often it takes tragedy to force us to confront our convictions.
Regardless of whether werewolves whet one's fiction palate, the plot of Fool Moon takes a backseat to its characterization. This isn't epic fantasy, where an orphan farm boy discovers he's the Chosen One and saves the kingdom (that would be Butcher's Codex Alera series). Fool Moon embodies the dark and gritty nature of the mystery and urban fantasy genres, which dictate that magic is serious business and somebody always gets hurt. Usually Harry. Because he always tries to do the right thing, and bad guys, for some reason, don't like that.