It’s All Relative: Adventures Up and Down the World’s Family Tree By A.J. Jacobs (Simon & Schuster, 295 pp. $27)

A.J. Jacobs’s latest book, It’s All Relative: Adventures Up and Down the World’s Family Tree, starts with an email he received that read: “You don’t know me, but you are an eighth cousin of my wife.”

His first reaction was that the note came from a swindler about to ask for cash to redeem a long-lost bank account, proceeds of which he would, of course, share. However, the message was legitimate. The writer had created a database that includes “about 80,000 relatives,” he informed Jacobs.

Jacobs’s DNA is clearly programmed to recognize a good book idea. Genealogy is hot. You can’t watch television without seeing a commercial for a service that will test your DNA and reveal your genetic background. There are multiple websites that help you create a family tree. So Jacobs went foresting.

It’s All Relative is well written, light-hearted and fun, as were Jacobs’s earlier best sellers, The Year of Living Biblically and The Know-It-All. Jacobs’s research reveals that he and his wife are distant cousins. (He’s also related to Joseph Stalin, John Wayne Gacy and the Rev. Jim Jones.) He finds a newspaper ad in which a great-uncle endorses a product that cured piles, which delights him, he writes, “since I have hemorrhoids myself.”

In fact, he discovers (spoiler alert) that we’re all related. Some scientists estimate humans share 99.9 percent of their DNA. Therefore, Jacobs concludes, if we knew we’re all cousins, we’d treat each other better. So he sets out to create a Global Family Reunion—a Guinness World Record of family reunions—to further his point.

Jacobs describes himself as a mutt. His DNA is a very small percentage Arab, which makes him happy. “I’m hopeful that embracing our genetic jambalaya will erode tribalism for all of us,” he writes. Yet Jacobs, a direct descendent of the Vilna Gaon, exudes Jewish tribalism at its best. He belongs to a synagogue, lights Shabbat candles, celebrates Jewish holidays and will have bar mitzvahs for his three sons.

It bothered me, however, that it didn’t bother him to hold his reunion on a Saturday, even when told that would prevent any Orthodox family from attending.

Still, there’s a touch of nobility to his efforts. Read this enjoyable tome and you might take up his cause.

Curt Schleier, a freelance writer, teaches business writing to corporate executives.