The novel explores the friction between different cultures and worldviews, primarily embodied in the Belseys and the Kipps. Howard Belsey, a white British Rembrandt scholar, represents a more traditional and somewhat out-of-touch academic perspective. In contrast, Monty Kipps, a Trinidadian-born art historian, challenges conventional art interpretations with his focus on social and political contexts. Their opposing viewpoints, both personally and professionally, create a dynamic tension that fuels much of the novel's conflict and intellectual debate. This clash is further amplified by the families' racial and cultural differences, exposing the complexities of identity and belonging in a diverse society.

'On Beauty' delves into the messy reality of love and marriage through the lens of both the Belsey and Kipps families. Howard and Kiki's marriage, already strained by years of unspoken resentments, is thrown into turmoil by Howard's infidelity. Their struggles highlight the challenges of maintaining passion and connection amidst the daily grind of family life. Simultaneously, their children navigate their own romantic entanglements, facing heartbreak, betrayal, and the complexities of interracial relationships. Throughout these intertwining narratives, Smith explores the themes of forgiveness, reconciliation, and the enduring bonds of family, even in the face of deep-seated flaws and betrayals.

True to its title, the novel grapples with the concept of beauty in its various forms – from art and music to human relationships and even seemingly mundane aspects of everyday life. Smith challenges traditional notions of beauty, suggesting that it can be found in unexpected places and often coexists with imperfection and pain. Through the characters' diverse perspectives on art, music, and personal aesthetics, the novel prompts readers to question their own definitions of beauty and its significance in a world often obsessed with superficial appearances.