Murder on the Serpentine by Anne Perry 288 page.
This is #32 (!) in the Charlotte and Thomas Pitt series by Anne Perry, and I believe it will be the final book in this series (from what I saw in a review). I feel like in her last few Pitt and Monk series books, Anne Perry's heart just didn't seem to be in writing. However, this book measured up to the books I have enjoyed that are earlier in this series.
In this story, Thomas Pitt, Commander of Special Branch, receives a summons from the Queen. The body of Sir John Halberd, the Queen's confidant, has been found in the shallow water of the Serpentine in Hyde Park. At first dismissed as an accident, Pitt is sure that Halberd has been murdered. At the time of his murder, Halberd was conducting a surreptitious investigation of Alan Kendrick, a man who seems to have an undue amount of influence on the Prince of Wales. Now, Pitt must navigate his investigation with the utmost discretion and stealth to determine who murdered Halberd, and what secrets he had been about to uncover at the time of his death.
This story ties into the politics of the time, especially the Boer Wars (it is set between the first and second Boer War). I found the addition of the information about the war, as well as Britain's interests in South Africa, to be really interesting. Perry does a nice job with slowly increasing the pace here, so that there's a feeling of danger which keeps building through the story. I also appreciated that Charlotte Pitt, Thomas' wife, has more of a role in this story. I felt that by the end, I was satisfied and if this is actually the end of this series, I don't feel like I have unanswered questions or feel that it's too abrupt of an ending.
It does help to be familiar with the series before starting this book, although the book can stand alone pretty well. However, you have more context for a lot of the story and character motives if you've been reading the series all along.