The Tin Flute (French: Bonheur d'occasion, which literally translates to "Secondhand happiness") is a 1945 realist novel written by Canadian author Gabrielle Roy. Set in Saint-Henri, a slum neighborhood in Montreal, during WWII, the novel tells the story of a young waitress by the name of Florentine Lacasse, who dreams of a better life for her and her family.
This hope for a better life, as well the harsh reality of both the situation and the environment, is actually one of the main themes in the novel. Most of the characters are poor, desperate and struggling to find happiness, which they often believe comes in the form of money and wealth. Thus, poverty, the struggles of the working class and the far-from-ideal living conditions in Saint-Henri are often discussed in the The Tin Flute:
A crowd of ragged children were playing on the sidewalk among the litter. Women, thin and sad, stood in evil-smelling doorways, astonished by the sunlight. Others, indoors, set their babies on the windowsill and stared out aimlessly. Everywhere you saw windows plugged with rags or oiled paper. Everywhere you heard shrill voices, children crying, cries of misery coming from the depths of this house or that, doors and shutters closed, dead, walled up against the light as if it were a tomb.
Florentine, for example, despite being poor and miserable, doesn't lose hope that she will one day live a good life:
In her heart the need to live in spite of everything found its expression in a stubborn defiance. This was not the end. Because she couldn't have what she wanted, she refused whatever was offered: but there must be miracles, she thought, for people like herself, bold and self-sufficient. Her eyes, heavy with sleep, were fixed on the thin ray of sunlight growing stronger in the room.
She wants to be wealthier, happier, and to find romance. She falls in love with the arrogant and selfish engineer Jean Lévesque, who desperately wants to live in Westmount, the rich neighborhood in Montreal; he shares Florentine's ambitions of getting out of poverty, but ends up shattering her dreams about a romantic life when he rapes her and gets her pregnant.
In the end, Florentine ends up sacrificing her happiness for comfort and financial stability—she settles with Emmanuel Létourneau, a wealthy and kind soldier, who's more than happy to provide for her and her child, as, unlike Jean, he actually loves her. In this context, love is also an important theme in the novel:
This is my wedding day! The day I marry Emmanuel! And the word "wedding," which she had always linked the happiness, now seemed austere, distressing, full of snares and revelations. She saw her mother, heavy and moving with difficulty. A vision of herself as a victim of the same deformity was vivid in her mind.
Another relevant theme might be loss, as all of the characters end up losing something—Florentine gradually loses her optimism, while her strong and resilient mother Rose-Anna loses the feelings of fulfillment and family love, especially when she compares the lives of her children with others. Her younger brother, Daniel, loses his health and, sadly and ironically, ends up experiencing the "better life" in the hospital in Westmount, only because he is dying of leukemia; her father, Azarius, loses all hope in humanity when he feels pressured to join the war in order to salvage his family and provide for them, as he cannot hold a job—despite being a global conflict, the war ends up being the solution to his problem.
The thematic representations of the novel are all interconnected, which is why writing a good thesis statement can be tricky; the thesis statement is essentially the most important part of an essay or a research paper, as it summarizes the main point that you're trying to make. To make a strong thesis statement, you need to focus on one main idea or one main topic and the body paragraphs should provide evidence to support the thesis statement.
For example, you can ask yourself, how does the desire to experience wealth and comfort motivate the characters in The Tin Flute? Does their ambition and struggle to survive affect their life choices? In this sense, one thesis statement you may consider writing could be focused on the main characters' pursuit of happiness.