I haven't actually read that one, but I did come across a detailed review that spilled the beans on the main players. The protagonist is almost always someone who has retired from some dangerous life—a legendary hitman, a disgraced special forces operator, or a secret society member—and just wants to run a coffee shop or be a librarian. Their entire struggle is resisting the call back to action. Then you have the obligatory love interest, usually the girl next door or a new coworker, who represents the normal life they crave but also becomes the reason they can't stay hidden.
There's always a figure from the past, a former comrade or sworn enemy, who tracks them down and drags them back into the fray. Sometimes it's a younger sibling or a protégé in trouble. The antagonist is often a corrupt official or a crime lord who underestimates the 'ordinary' person they're threatening. The character dynamics are pretty standardized, but the fun is in seeing how long the facade can hold before the carefully constructed quiet life explodes.