A.J. Jacobs has received some strange emails over the years, but this note was perhaps the strangest: "You don't know me, but I'm your eighth cousin. And we have over 80,000 relatives of yours in our database."

That's enough family members to fill Madison Square Garden four times over. Who are these people, A.J. wondered, and how do I find them? So began Jacobs's three-year adventure to help build the biggest family tree in history.

Jacobs's journey would take him to all seven continents. He drank beer with a US president, found himself singing with the Mormon Tabernacle Choir, and unearthed genetic links to Hollywood actresses and real-life scoundrels. After all, we can choose our friends, but not our family.

"Whether he's posing as a celebrity, outsourcing his chores, or adhering strictly to the Bible, we love reading about the wacky lifestyle experiments of author A.J. Jacobs" (Entertainment Weekly). Now Jacobs upends, in ways both meaningful and hilarious, our understanding of genetics and genealogy, tradition and tribalism, identity and connection. It's All Relative is a fascinating look at the bonds that connect us all.