Mia Winchell is a thirteen-year-old girl who sees sounds and letters as having colors. At first she doesn't tell anyone because she doesn't want to be seen as a freak, but when her condition starts interfering with her schoolwork, she decides to tell her parents about it. Mia is diagnosed with synesthesia, and the story follows her as she learns to accept herself.
A Mango-Shaped Space contains examples of:
- Candlelit Bath: Mia reads online that taking a hot, candlelit bath will enhance her experience with synesthesia. She tries it while listening to music and finds that the steam does make the colors seem deeper and more intense.
- Celebrity Resemblance: Mia's mom says that Jerry Weiss, the neurologist who diagnoses Mia with synesthesia, reminds her of Paul Newman. Mia says, "The salad dressing guy? No way!"
- Cradle of Loneliness: After Mango dies, Mia sleeps holding his favorite toy, a stuffed Tweety Bird.
- Dead Man Writing: Mia's best friend Jenna Davis's mom died of cancer three years ago. When she realized she wouldn't get to see her daughter's next birthday, she made a bunch of packages, each consisting of a present and a long letter about her life. She entrusted the packages to Mia's mom, who gives one to Jenna each year on her birthday.
- Everybody Hates Math: Math has always been Mia's worst subject. She especially struggles with pre-algebra because she has trouble thinking of X as being equal to a number when that number isn't the same color as X. At a synesthesia meetup, she meets people who had even worse problems with math because they saw numbers as having personalities and felt guilty about pairing up numbers that didn't get along.
- First Kiss: Mia meets a 14-year-old boy named Adam Dickson through the synesthesia mailing list. They share a kiss at the meetup. She regrets wasting her first kiss on him after he sends her an insensitive email about Mango's death.
- First-Name Basis: Jerry insists on being called by his first name and corrects anyone who calls him Dr. Weiss.
- Granola Girl: Mia's sixteen-year-old sister Beth spends a summer in California. When she comes back, she's taken up witchcraft, become a vegetarian, and developed an interest in yoga. Mia is confused, but their superstitious eleven-year-old brother Zack is happy because Beth now shares some of his weird beliefs about the energy of the universe.
- Happy Rain: Mia loved playing in the rain when she was younger. Then she saw lightning hit a tree, which scared her enough that now she usually stays inside when it rains.
- It's All My Fault: Mango was born with a rip in his lung lining and isn't supposed to be outside in cold weather, but he manages to escape one night and is stuck outside for several hours. He dies that night. Zack and Mia both blame themselves for his death, Zack because he thinks he's the one who let him out and Mia because she got so wrapped up in her own life that she didn't notice he was missing. Their parents tell them that Mango had stopped eating even before he was stuck outside, which means that he was probably already dying and it wasn't the kids' fault.
- Lost Pet Grievance: Mia takes her cat Mango to the vet. Her classmate Roger Carson is also there with his elderly Golden Retriever, who is about to be put down. Mia hears Roger sobbing from the examination room. He comes out crying and clutching the dog's leash to his chest. Months later, Mia experiences this when Mango dies. She's so devastated that her synesthesia temporarily goes away.
- Middle Child Syndrome: Before Mia is diagnosed with synesthesia, a therapist speculates that she's acting out because she's jealous of the privileges Beth enjoys and the attention Zack gets. Mia knows that's not true.
- Parental Marriage Veto: Mia's mom is estranged from her parents because they disapprove of her marrying beneath her station and living in rural Illinois.
- Parent with New Paramour: Jenna's dad has a new girlfriend named Rebecca. Jenna doesn't like her, even though her dad accuses her of hurting Rebecca's feelings. Late in the book, Jenna's dad breaks up with Rebecca.
- Prefers Going Barefoot: Mia doesn't like wearing shoes and would rather be barefoot at all times. Her dad nicknames her Wild Child because of it. In the first chapter, when she notices her shoes are untied, she doesn't bother tying them, and instead takes them off and throws them over her back.
- Secret Path: Mia's father and grandfather built the family home together, with different visions of how it should look and no real plan. As a result, it has lots of hidden nooks, secret passageways, and stairs inside walls. Once Mia and Jenna used a secret passage to sneak into Beth's closet and eavesdrop on a slumber party.
- Sensory Overload: Mia sometimes suffers from this in noisy environments because of all the shapes and colors.
- Too Unhappy to Be Hungry: After Mango dies, Mia barely eats for the next few days. When she does manage to choke down food, it tastes like wet cardboard.
