The novel is actually split between Anna’s tragic romance with Vronsky and the moral/agricultural journey of Konstantin Levin.
Tolstoy covers far more than romantic scandal. He fills the pages with his personal views on: Deep discussions about faith.
Beyond the Affair: Understanding the Subtitle of Anna Karenina
The novel serves as an exploration of the "wages of sin" in a judgmental society.
When you pick up Leo Tolstoy's masterpiece, Anna Karenina , you are likely expecting a dramatic tale of forbidden love and scandal. While the story delivers on that, the novel's title—and its often-overlooked subtitle/description—tells a much deeper, more complex story about 19th-century life, psychology, and social change.
While often simply published as Anna Karenina , Tolstoy actually considered it a "roman" (a novel), which during his era was deeply connected to stories of adultery, social scandal, and entertaining scandal for the reader. 1. It’s Not Just Her Story
It is a common misconception that the book is strictly about Anna. As noted by Brian's Blog , the title is actually somewhat misleading.
Discussing the massive shifts in the characters' lives makes the 800+ pages much more enjoyable. My Special Relationships with “Anna Karenina”