Spit­ting in a vial or swab­bing your cheek and then send­ing it off for DNA test­ing is fre­quent­ly done with casu­al curios­i­ty. Peo­ple are often excit­ed about the prospect of dig­ging into their genealog­i­cal past. Tele­vi­sion shows like PBS’s Find­ing Your Roots and sto­ries from friends and neigh­bors who’ve dis­cov­ered new cousins across the coun­try or traced their ances­tors back to exot­ic loca­tions only enhance the allure.

The genet­ic test­ing mar­ket has explod­ed in just a cou­ple decades to include tens of mil­lions of people’s genet­ic fin­ger­prints. Lib­by Copeland in The Lost Fam­i­ly, calls the peo­ple pulled into the world of DNA test­ing ​“seek­ers.” She writes, ​“They are peo­ple obsessed with fig­ur­ing out just what’s in their genes.” Curios­i­ty and sense of iden­ti­ty fuel the seek­ers. Because it’s so easy — and fun — those who send off their DNA don’t always ful­ly under­stand the ram­i­fi­ca­tions of fig­ur­ing out the sto­ries in our genes. Peo­ple can find truths they aren’t pre­pared for; they can uncov­er secrets that might be more painful than sur­pris­ing. Copeland presents riv­et­ing exam­ples that span the spec­trum of what DNA test­ing can yield. Some peo­ple find rel­a­tives who fit into their life like a miss­ing puz­zle piece. Oth­ers find rel­a­tives who wish they hadn’t been found. Mis­takes have been made, too; found rel­a­tives turn out to be unre­lat­ed after all.

Trac­ing the his­to­ry of DNA test­ing, Copeland takes the read­er to the first DNA test­ing company’s head­quar­ters in Hous­ton. She shares a rare tour of the biggest DNA test­ing com­pa­ny in Utah, where she also spent time in the archives at the biggest genealog­i­cal library in the world.

The thread woven through the book is the sto­ry of Alice, a tech-savvy seek­er who dis­cov­ers that her father wasn’t who he thought he was. He was told that he was an orphan of Irish descent, adopt­ed and raised in a Catholic fam­i­ly. But when Alice’s DNA comes back show­ing that her her­itage is half Ashke­nazi Jew­ish, she com­mits to dis­cov­er­ing how that could have hap­pened. The sto­ry has all the ele­ments of a great mys­tery, full of seem­ing dead-ends and unex­pect­ed plot twists.

Even if some­one hasn’t per­son­al­ly spit in a tube and sent it off, this deeply-report­ed and well-writ­ten book mat­ters. It’s very like­ly that enough of all of our rel­a­tives have done so that any­one can be found using a process of ​“tri­an­gu­la­tion.” This method is how DNA has led to appre­hen­sions in a num­ber of cold crim­i­nal cas­es. It also has seri­ous con­se­quences for pri­va­cy that few of us have ful­ly considered.

Copeland writes, ​“This is the sto­ry of the seek­ers, who are grap­pling with ques­tions about iden­ti­ty. What makes us who we are?” Whole gen­er­a­tions are now able to ask the kinds of ques­tions they nev­er expect­ed they’d be able to answer. The Lost Fam­i­ly ably puts those ques­tions in context.