The last two lines of the book are "Look where your hands are. Now." Whoa.
Let's start by remembering Jazz's preoccupation with history. Violet and Joe are two individuals that are under siege by their own histories: Joe is perpetually a lost boy hunting his mama, and Violet is so terrified of becoming crazy like her own mom that she decides against having any babies. They're also part of the Great Migration, a huge historical event that saw thousands of black people move out of the post-Civil War South and into less hostile Northern cities. Except, of course, they couldn't completely flee racism or the past.
At the end of the novel, Joe and Violet have decided to let the past be the past and forgive each other for their bad choices and craziness—they've decided to stop living in the past and concentrate on the now. And where are Joe and Violet's hands at the end of the novel? Touching each other with the tender love of a long marriage. Aw… Joe and Violet 4 Ever.
So the last lines of the novel are both a reminder of where Joe and Violet are by the end and a warning to the reader: Remember the past but don't let it haunt you. Much as our hands have always been with us—much as we can all carry the past forward—so, too, are they with us now.
The narrator spends the last four paragraphs of the book talking about how nice lasting marriage is, and how s/he (who is this narrator, anyway?) wishes s/he had somebody to love. At the end (literally), Jazz is about all sorts of love: romantic, familial, maternal, paternal, friendship. All relationships are complicated, but they're also all worth it.