Loneliness
The protagonist of Solitaire, Tori Spring, is a teenage girl who feels disconnected from the world around her. Although she once had a good group of friends and fit in well with everyone, she now struggles to form meaningful relationships with other people. At the start of the novel, she doesn't have any real friends and spends much of the time by herself (by her own doing). The novel explores the idea that, despite being surrounded by people, someone can still feel alone. Though Tori eventually finds someone with whom she connects in Michael, Tori still goes through periods of loneliness as she struggles to figure out who she is and where she belongs in the world.
Mental health struggles
Mental health struggles are an important theme in Solitaire. Throughout the novel, Tori struggles with depression and anxiety, depression and anxiety which sometimes cripples her. Much of the novel is devoted to the struggles that Tori and other people with mental health conditions face in their attempt to heal. The theme of mental health struggles highlights the importance of seeking help and support when someone is struggling, especially those who are suffering in silence. It also shows the ways that a person's mental health can dramatically impact a person's life and the way they live their life.
Becoming an adult
At the start of Solitaire, Tori is on the precipice of becoming an adult. She is almost done with high school and will presumably start college soon. As such, she has quite a few decisions to make about what she will do in the future—decisions only an adult could make. Another part of Tori's journey toward becoming an adult is her questioning her identity. She is questioning her sexual orientation and must embark on a journey of self-discovery and self-acceptance so that she can enter the adult world confident in herself, her identity, and her abilities as a woman.
Harrasment
To escape reality, Tori turns to social media and technology, a world that she immerses herself in to escape from her pain. Through Tori's experiences, the reader is shown the negative effects of online harassment and the pressure to present a perfect image to the world. But people aren't perfect, and those images can be harmful. And when someone doesn't present a perfect image, as Tori doesn't, they are ridiculed and harassed for being different and for sticking out.
