When The Party Died gives us our first real glimpse at Brock's wife Laura, at her career and at other complications in their relationship (beyond the very singular focus of the couple's problem in first two books). The plot soon zooms delightfully between an art gallery and a country manor, with an enormous amount of potential clues—and, like the reader, the investigators have no idea what they mean.
It's a great setup for the main plot, which kept me interested throughout, and satisfied with the reveals. It's one of the few mysteries I've read lately in which I had no idea who did it, but looking back, there were plenty of clues.
The subplots were a bit less effective; Poole is now at a point where he's just an idiot for not being more forward with the intelligent young female constable who's so into him, she's being threatened with Perfect Girl Syndrome. (It's an interracial relationship, which no one seems aware of in the book, which struck me as more than a little odd. Certainly it's not that big of a deal, but when Poole meets Sanders' Indian mother, Barnett seems to go through contortions not to mention it.) The climactic scene reveals something quite delightful about her character. I hope Barnett continues to show us her multiple dimensions in future books.
The continuing subplot of Poole's mother and father are getting diminishing returns for me as well, but there wasn't much of it in this installment.
One nitpick: there were a lot of typos and grammatical errors in this book—inconsistent use of punctuation, names spelled differently (Frazer and Fraser, especially). It was a bit distracting, but not enough where I ever considered abandoning the book.
Overall, a worthwhile read, and one that has me waiting until the day I can pre-order the fourth book in the series.