Every Last Secret upholds many of the common conceits of the psychological thriller genre. The unreliable narrator is one example. The narrative alternates between Cat’s and Neena’s first-person perspectives. Only as the narrative develops does it become clear that Cat, concealing the truth of various actions—such as poisoning herself with antifreeze and blaming Neena—is a highly unreliable narrator. Only toward the end of the book does the reader learn how unreliable Cat’s narration has been.

The antifreeze incident is an example of a red herring, or a false clue, another element typical of the thriller genre. Throughout the book, Cat sprinkles fake clues designed to frame Neena. However, these red herrings also mislead the reader. While the narrative includes many false clues, it also includes real ones. Many mystery-driven thrillers provide a mix of fake and real leads, and the reader must identify which clues are authentic. One example of a real clue is Cat’s admission that she stole a key from the former next-door neighbor’s house; the stolen key later gives Cat the power to plant false evidence in the Ryder home.

As a psychological thriller, Every Last Secret also explores Neena’s and Cat’s psyches.