I’ve burned through the entire Mick Herron Slough House (Slow Horses)collection and need something to scratch that same itch

I just burned through the entire Mick Herron Slough House (Slow Horses) collection — yes this includes novellas and spinoffs. I'm in dire need of additional good page turning espionage fiction.

I tend to like spy fiction that has strong characterization and/or great attention to detail/realism. Herron's work mostly hit that intersection of both. Already done most of the output from John Le Carre, Len Deighton, Eric Ambler, Robert Littell, and Graham Greene to give you ideas of what else I've enjoyed.