To quote The Princess Bride, marriage is what brings us together today – and every day, in Sense and Sensibility. Basically everything in this book – plot, the characters, their various motivations – all boil down to marriage. As the most important social contract of the world that Austen depicts, marriage is an all-important concern. Who's marrying whom? Why or why not? Is it a good match, or a bad one? Marriage isn't just a personal matter – it practically concerns everyone in a given social group. Why? Well, marriage isn't just an issue of love or companionship, the way we think of it now; instead, it was more akin to a political, social, and economic alliance between families. When two people decide to get married here, it's not just between the two lovers – it's between them, their parents, their siblings, and their hundred closest friends.
The resolution of the love plots is necessarily the end of the novel; Austen is simply not interested in matrimonial life.
As a middle ground between the economically motivated marriage (such as Willoughby's) and the love marriage, Marianne's match with Colonel Brandon problematizes the otherwise happy ending of this book.