In March 2008, Barack Obama made headlines.

Not for his town hall speeches or his Super Tuesday performance. Instead, they focused on a photo of the then-Senator in Kenyan dress.

An Internet-fueled controversy was born. Some people called it a smear campaign. Others claimed it proved Obama wasn’t a U.S. citizen, making him ineligible for the presidential race.

The truth came out eventually: The snapshot was taken two years earlier, when Obama was on an official visit to Kenya. He visited the place where his father, Barack Obama Sr., was born.

Even after the Kenyan-dress kerfuffle died down, this side of the president’s heritage has remained mysterious. His father was a member of the Luo tribe in Kenya, and Barack Obama Sr.’s ancestry — a tribal tradition that goes back centuries — has been relatively little explored.

In “The Obamas: The Untold Story of an African Family,” author Peter Firstbrook attempts to piece together oral history, fables and traditions to explain the deepest roots in the Obama family tree, a lineage that even the president knows little about.

It’s a huge undertaking, but Firstbrook manages to do it with ease. Despite some stilted writing, he uses skills honed as a documentary filmmaker to unravel a compelling story about the Obama family in Kenya that much of the media has glossed over.

On Inauguration Day in 2008, while journalists staked out the compound of Sarah Obama, step-grandmother to the soon-to-be 44th president, Firstbrook sat with more than 500 people, all members and friends of Obama’s extended family, at the compound in K’obama. No other “mzungu,” which means white man in Swahili, was there.

The book gets off to a slow start. Firstbrook delves into details about how the Luo, the third biggest tribe in Kenya, arrived in the region. While the tales of who begot whom may seem dull after a while, his descriptions of tribal traditions are captivating.

For instance, unlike in other African cultures where circumcision is a right-of-passage ritual, the Luo pull six teeth from the bottom of the mouths of both girls and boys. And according to Luo beliefs, a person cannot visit their in-laws’ home if they die until after the burial because seeing the corpse would be “to see them naked.” A man cannot look at the ceiling if he goes to the house of his wife’s parents. In-laws can’t accept food or stay the night when they visit. So when Obama invited his mother-in-law, Marian Robinson, to live in Washington, D.C., with his family, it broke the tribe’s taboo. According to the tribe’s tradition, the only way to fix the trespass would be to knock down the family’s home — in this case, the White House.

In describing the Luo personalities, Firstbrook seems to draw comparisons to Obama. Although he doesn’t make the explicit connection, he might be describing the president in this passage: “The Luo, Obama’s African tribe, are known for being easygoing and generous, and I had received nothing but help and support from them. But they also had a reputation for, among other things, talking big and doing very little.”

And later the description seems to echo Obama’s call for transparency in government: “The Luo are fair and they are democratic people. They want to discuss issues. They don’t want secrecy. They don’t have ‘night meetings.’ If they call a meeting, they will reveal it outside when they’ve done.”

The narrative gets more fascinating when Firstbrook describes Obama’s grandfather and father. Hussein Onyango Obama, father to Barack Obama Sr., was a forceful man who fought in both world wars.

The president’s father also showed willfulness. At age 9, he ran away from home only to be returned several days later. He found school easy, according to Sarah Obama: “He came back after the first day and told his father that he could not study there because his class was taught by a woman and he knew everything she had to teach him.”

The book also describes the reverence that those in the Luo tribe have for the president. From schools named after him to a note on his great-grandfather’s grave (“Dedicated by the Barack H. Obama Foundation”), the president’s influence is strong in the region.

Firstbrook best shows this when he describes visiting the place where Obama stayed when he came to for Kenya for the first time. The hut was small with wooden shutters.

“I want to show you something special,” Firstbrook’s guide said to him. “This house is where the president slept. … He came visiting — he wanted to know his roots. So he came up to Kendu Bay, and this is where he slept.”