Slow Horses (Slough House), by Mick Herron

A building in London houses damaged spies. When members of the British intelligence services become alcoholic, make major errors, or otherwise wash out they are sent to Slough House, a nondescript building in London. Those who end up here are known as the slow horses. They know too much to be sent into the real world, but are too damaged to have assignments of any value.

River Cartwright is one of these. His grandfather, the OB (Old Boy) was in the service. Despite that lineage he heads up a training exercise that gets completely screwed up. That gets him sent to Slough House where the days slug by with little to do but makework. He’s surrounded by other outcasts all ruled over by a gassy, cranky chief.

Meanwhile in London the son of immigrant Pakistanis is taken by a militant group of anti-immigration thugs. Their plan: To behead the young student on a live video feed to show the world that Brits can be as ruthless as other terrorists. While the whole of Britain tracks the story on the news River is drawn into it all when a journalist with ties to the alt-right groups, whose garbage River has been assigned to inspect, ends up dead.

As the investigation progresses it becomes clear to River and the other slow horses that there’s a more complicated plot going on, one that draws them all into an effort to rescue the kidnap victim.

It’s a compelling story about people who wanted to dedicate themselves to the security of their country … there are several references to 7-7, London’s 9-11 when trains were bombed on July 7, 2005 … but couldn’t cut it or couldn’t navigate the politics. The events in the book bring them together as a functioning team, despite their chief’s assessment that they’ll never overcome their shortcomings. It’s a fun thriller that gets the reader rooting for the whole team as they try to outwit some really horrible bad guys along with their own service.

This is the first book in what is now a series of four books. This one was published in 2010 and won the CWA (Crime Writers of America) Golden Dagger award. This is a good place to start in order to keep tabs on the various characters and their relationships to the agency.