Memento
Nolan feels like he's been defined by everything after 2010, with Inception being the inflection point, but honestly, I feel his run of movies in the early to mid-2000s is a much more interesting time for him. He takes big swings around themes centered around pretty baseline concepts (love/family in Interstellar, memory/dreams in Inception and here, time with Tenet, etc.) and except for Oppenheimer really, he sort of leaves those ideas there.
But his work pre-Inception, I feel, operates with such nuance that his blockbusters don't necessarily have; taking the hazy, unreliable nature of memory, combining that with an unreliable narrator whose quest is founded on the already erratic emotions of anger and love. Doing all of that while still understanding that memory is the foundation for the perception of our world. And it's cool!
I don't know. Nolan has such a distinct and interesting filmmaking career, and watching this makes me wonder if he'll ever return to this level of writing.