The Incident of the Book in the Nighttime by Vicki Delany
This time around Gemma and the gang are in London for her sister, Pippa's, wedding. Her ex-husband, Paul, asks her to meet him in his bookstore to see a rare used book, but when she and Grant arrive, they find him dead in his office. Gemma feels like she owes it to Paul to help find the killer.
I've read enough of the series to know most of the characters so I didn't feel overwhelmed by all the people we only meet briefly before they get sidelined for most of the story.
Gemma and friends traipse all over London, to mansions and nightclubs and coffee shops. The clues lead in several directions, but at the same time Pippa is dealing with a government situation and it's no surprise when Gemma's case and Pippa's job overlap. The story is a little far-fetched and the motive a little weak, but I enjoyed it nonetheless. I would rather have been on the Holmes...