I really, really liked the 1st two wolf books, and I thought the Wolf King was pretty good. I would call this one pretty good, as well. Definitely worth reading, a lot more magical elements than the 1st series. The characters split up quite a bit so I get a bit annoyed when I'm thinking about a character that doesn't show up for 75 pages, and I was a touch annoyed that there wasn't more resolution by the end, since the 3rd book isn't out yet. But not to the level of WOT or anything.
I thought it interesting that both this book and the new King Arthur movie that's coming out this summer both emphasized Guinevere as a celtic warrior princess. Makes her much more interesting.
What I love about Borchardt is that her research is rock-solid, and her characterization of historic figures is so strong, they begin to define how I feel about that person. Her Caesar is so compelling, I have a hard time separating her character from the historical figure.