The title seems simple at first glance, but the deeper we get into the novel, the more it resonates.
The Jewish people are sometimes called "The Chosen People," and the title obviously draws on this often-misunderstood epithet. Here’s a link to an article that gives some explanation of the phrase. As the article points out, some people think the term "The Chosen People" means "the chosen race." But it can’t possibly mean that, because Judaism is not a race, any more than any other religion is. In fact, there are Jews of all different races. What’s more, anyone can choose to become a Jew. Sure, most Jews are born into Judaism, but, even if a person is born into it, he or she must choose to what extent he or she will practice it, if at all.
At its bottom, the phrase "The Chosen People" means that Jews are chosen to try to make the world a better place. Not by trying to turn other people in to Jews, mind you, but by studying and doing good works — be it planting trees or helping the homeless. A person who chooses to become or remain a Jew takes on that burden, to whatever degree.
The title also refers to a Talmudic maxim, which states that a person should choose not only a teacher, but also a friend, as David and Reuven discuss, and with friendship comes great responsibility. When Reuven chooses to befriend lonely, brilliant, and conflicted Danny, the choices he makes can help either free or enslave his friend.
And that’s really what the novel is all about – the freedom and responsibility that come with the choices we make. Reuven, David, Danny and Reb Saunders are constantly bombarded with difficult choices, both in terms of each other and in terms of the larger world around them. When World War II ends and its horrors are revealed, their choices take on life-or-death significance. What the characters have chosen will change their lives forever.