The good in the story is how Gilman has picked a theme - a brand of magic (as it were) - and makes it robust enough to encompass all of the kinds of magic use that she wants to describe. Her version of magic relies on electricity to function, and so everything is in terms of current and power. This is not the Harry Dresden "electro-mechanical things don't work around me" kind of current, but more of the "put your protection spell into the house wiring" version. Gilman also divides up the magic users into the toe-the-line/join-the-club, the lone rangers (for whatever reasons), and those who have become addicted to the raw source of current and have lost control (rather like drug addicts).
The book's biggest flaw is Gilman's addiction to avoiding names. She likes to describe scenes that are outside of the heroine's view without names, as though this will make them stay a secret longer, or puzzle the reader as though we were the heroine. It only served to frustrate me, as I wasn't really sure where I was in the story. At one point Gilman deigned to drop a name, and I had to backtrack halfway back to figure out if I had met that character previously (I had). It was a tad frustrating, and quite unnecessary.
The heroine's humor, and her emotional angst, are well done but not overdone. Gilman gives her the character depth of anxieties and deep thought as well as temper tantrums and sarcasm. Part of humor is timing, and despite being an anecdote inside of the story, the method of how one of the character's names is introduced as a snap-crack at a passerby hit my funny bone straight on. The thought of polar bears in New York just made me giggle. It was almost a classic Anita Blake line, or a Diana Tregarde one, if she were to swear like that.
Deep? No. Fun? Yes. I'll recommend this one for beach bag reading. It's long (411 pages in paperback) but a fast reading with big print.