Who is Barack Obama?

That's a question usually answered before a president is elected. But in 2008, Americans eager for change sent to the White House a charismatic junior senator from Illinois who had emerged on the national stage just four years earlier.

After a year in office, in one of the first of a coming flood of Obama books, David Remnick attempts to do more than simply recount the distinctive life story of the 44th president.

In "The Bridge," Remnick, editor of The New Yorker, also aims to place Obama in the context of America's struggle with race — especially the tumultuous 50 years that began amid civil rights protests and ended with the election of the first African-American president.

The inside of the book's front cover is a photo of the 1965 civil rights march on the Edmund Pettus Bridge in Selma, Ala., on "Bloody Sunday." The inside of the back cover: the panoramic scene on the Capitol steps at Obama's inauguration 44 years later.

In between, this sprawling, ambitious book chronicles Obama's role as a sort of human bridge, a transitional or even transformational figure.

"Obama is what comes at the end of that bridge in Selma," civil rights icon John Lewis said.

It is not a role that Obama, presenting himself as a leader who just happens to be black, has chosen to highlight. During the presidential campaign, Remnick writes, race "was the thing always present, the thing so rarely named."

Before then, though, Obama faced his own struggles with race, with figuring out where he fit. Remnick explores the racial cross-currents in Hawai'i, where Obama was born; the independence movement in his father's Kenya; the dynamics in the mostly white halls of Harvard Law School; the internecine racial politics of his adopted Chicago.

He is "the interpreter," as friend Cassandra Butts puts it — his biracial, bicultural birth and upbringing making him skilled in building a bridge between races.

This 656-page book is beautifully written and exhaustively researched, and includes interviews with Obama. Remnick paints on a bigger canvas than Obama did in his 1995 memoir, "Dreams from my Father," and offers fuller portraits of his absent father and peripatetic mother. And, while Obama's rise still seems astounding, the author makes it clear it was not accidental — it's the result of ambition and, well, audacity that were sometimes masked by Obama's calm demeanor.

Remnick explores the roots of Obama's elusive cool, the aloof self-confidence that makes him "no-drama Obama" during crises. Those qualities were tested in the recent health care debate — and will surely be tested again.