The Shadow Cabinet by Maureen Johnson
"Rory and her friends are reeling from a series of sudden and tragic events. While racked with grief, Rory tries to determine if she acted in time to save a member of the squad. If she did, how do you find a ghost? Also, Rory’s classmate Charlotte has been kidnapped by Jane and her nefarious organization. Evidence is uncovered of a forty-year-old cult, ten missing teenagers, and a likely mass murder. Everything indicates that Charlotte’s in danger, and it seems that something much bigger and much more terrible is coming.
Time is running out as Rory fights to find her friends and the ghost squad struggles to stop Jane from unleashing her spectral nightmare on the entire city. In the process, they’ll discover the existence of an organization that underpins London itself—and Rory will learn that someone she trusts has been keeping a tremendous secret."- summary from Amazon
I absolutely adore this series from Johnson. It's sarcastic/funny just like her other books, but also very dark, very thought-provoking, and very supernatural. While I was not a fan of the two-year wait between the last book and this one, it was definitely worth the wait as the book is simply fantastic. The series as a whole is breath-taking and awesome, and I am really looking forward to the final book whenever it comes out.
FTC: Borrowed book from library. Link above is an Amazon Associate link; any profit goes toward funding contests.