The following version of this book was used to create the guide: Montimore, Margarita. Oona out of Order. Flatiron Books, 2020.

Oona out of Order follows the nonlinear life of Oona Lockhart as she jumps in time each New Year's Eve. The novel is divided into nine parts, after Part 1, each begins on New Year's day as Oona adjusts to her new life and follows her adventures through the year. The omniscient narrative voice is interjected with snippets of Oona's inner thoughts.

In Part 1, Oona was on the brink of turning nineteen. She rang in the new year at a party in Brooklyn. As the evening progressed, Oona was increasingly distraught about the decision she would have to make; unsure if she should go on tour with her band, Early Dawning, or live in London with her friend Pam. Her boyfriend, Dale, gave her a leather jacket and fervently kissed her on the dance floor. As the New Year's Eve countdown began Oona felt tipsy and out of body. She was afraid of making the wrong decision and wished she didn't have to decide at all.

Part 2 began with Oona coming-to in an unfamiliar room. She was confused by the dim lighting and young man who introduced himself as Kenzie. He explained that this was her first jump in time and gave her a letter from her future self that explained the odd circumstances. Every year on New Year's Eve Oona leaped into a different year in her life, it was now 2015. Despite seeing a much older version of herself in the mirror Oona was in denial. Oona spent the year adjusting to her new environment, listening to music and spending time with Madelein. She anxiously awaited New Year's Eve, hoping that she would leap back to an earlier year in her life.

Oona's jump in Part 3 brought her to 1991. She woke up in a club, high on an unknown substance. She flirted with a curly-haired stranger and had sex with him, unaware that a note in her pocket warned her not to. Her future self had left the note to warn her that she was at the party with her boyfriend Crosby. When Oona found Crosby in the crowd she was unsure how to act. She knew her future self was in love with him but she had no emotional attachment. Crosby immediately ended their relationship when he discovered that Oona cheated on him. Oona was discouraged and decided to numb out. She spent the year getting high and partying. She stopped playing and listening to music in favor of snorting ketamine and having sex with strangers. As the new year approached Oona's highs were less effective. She resolved to spend the next year sober.

In Part 4 Oona met her husband Edward. She struggled to feel in love with him but tried to take her earlier self's advice and work on the relationship. Edward was distracted with opening his restaurant, Clary's Pub. Oona filled her down time by taking guitar lessons, something she had wanted to do for years. She was attracted to her instructor, Peter, but by the time she was divorced and asked him out, Peter was in a relationship. Oona was eager for a new year. She wanted to jump into her past.

Oona's wish to be in the past was granted in Part 5 but only by a year. She had to face meeting Edward and experiencing the first year of their marriage. Oona was frustrated and tried running away to Egypt. Fate caught up with her and she met Edward on the plane to Cairo. Intrigued by their emotional connection Oona gave in to dating and marrying Edward. Later in the year, Oona's suspicions that Edward was cheating with Francesca were confirmed. On New Year's Eve she went snooping in his office for more evidence. She found naked pictures of her husband and Francesca and her watch from Dale that had been stolen months before. Oona fled home, desperate to warn her future self not to get involved with Edward. Her attempts were futile and Oona jumped into a new year as the clock struck midnight. The next year, in Part 6, Oona travelled across Asia with Madeleine. She distracted herself from thinking about Edward by spending time on the beach and immersing herself in the foreign culture. She learned that you have to let yourself feel pain to learn and move on.

In Part 7, Oona woke up to find it was 1999. She asked her mother what the initials in her tattoo, M.D.C.R., stood for. Madeleine reluctantly confessed that the letters stood for Mackenzie Dale Charles Ray. She explained that this was Kenzie's full name. Oona gave birth to him shortly after Dale died but gave him up for adoption. Madeleine warned Oona that she was not allowed to have contact with her son but Oona was indignant and fled to Boston to find Kenzie. She disguised herself as a goth barista and bonded with Kenzie over music. At a dinner with Kenzie's adopted mothers, Oona accidentally revealed her tattoo and confessed her true identity. Kenzie was in denial and Oona flew back to New York to be with Madeleine. She longed for her next leap to take her to a year when her relationship with Kenzie was healed.

Oona's wish was granted in Part 8; she was reunited with her son. However, Oona's joy was dampened in 2017 by the death of Madeleine. She spent the year anticipating her mother's passing and grieving her loss. For the first time she understood that her time travel was a blessing. She would get to see her mother again when she lived in past years. In Part 9, Oona leaped back to the Brooklyn basement. She was elated to find that it was 1983 and Dale was still alive. She no longer felt torn by the decision in front of her. She was eager to spend as much time as she could with Dale and savor every moment as it came.