Although the two authors are very different, Anton Chekhov was born in Russia in 1860, and Nicholas Sparks is a contemporary American author, both men do write about the complex relationships between men and women, human interaction with all of its intricacies, tragedies and disappointment that exists in human relationships, particularly in romantic relationships.
They both also write about the choices that people make in their lives and the results, or consequences of those choices. Both authors write about sacrifice, the lengths their characters will go for each other, to be together, to care for one another.
Sparks writes love stories, but his stories are not the common, romance novels where there is a happy ending, there is triumph in love, and Sparks expresses the purity and joy of love in his books, but he also introduces reality into the stories, often one of his main characters will die, resulting in a short lived glorious love, enduring only in the memory of the character left behind.
In The Notebook, Sparks writes about a lifelong love story between Noah and Allie, young people who fall in love and end up in the golden years of their lives living side by side in a Nursing Home, with Allie suffering from Alzheimer's and unable to remember who Noah is, or anything but flashes from their long marriage.
In Chekhov's short story "The Lady with the Pet Dog," he writes about the unlikely love story of Dmitri Dmitritch Gurov and Anna Sergeyevna. Although Dmitri is a married man, he engages in physical relationships with other women, he has no love for his wife, his marriage is just a formality, a forced marriage, arranged by his parents. What Chekhov writes about is the unexpected case of true love being discovered when one least expects it.
Dmitri has no intention of getting attached emotionally to Anna, he goes on a vacation has a brief affair with her and then returns home to his wife and family. But when he returns home, he cannot stop thinking about Anna. He seeks her out, shocked to realize that he has fallen in love for the first time.