Christopher Nolan has earned the right to call his own shots but there was a time before "The Dark Knight" trilogy and "Inception" when he was still trying to make a name for himself. Ironically he did that with a film centered a man who couldn't even remember his own identity.
The cool and complex thing about "Memento" was that it was a film in reverse and focused on a man (Guy Pearce) out for revenge after the death of his wife. The twist though is that Pearce's character has a memory disorder where he can't make new memories so he relies on photographs and notes to remember what he uncovers. Of course the bigger twist turns out to be that Pearce is really chasing himself as he's ultimately the one responsible.
While it was legitimately a killer development, trying to piece together everything that happened is a fool's errand and likely will drive you nuts. To quote Lewis Black..."don't think about that for more than three minutes, or blood will shoot out your nose!"