Mick Herron is the genius behind the Slough House series.

This Is What Happened (2018) is a standalone novel. Quite different than the Slough House books.

I enjoyed it for being so different.

In London, Harvey Wells, an MI5 agent, recruits lonely 26-year-old mail room employee Maggie Barnes to spy on her firm.

What at first appears to be a tale of spycraft and intrigue turns out to be something entirely different.

Very well written. I recommend the book.