A new book about Michelle Obama reveals little-known details about the first lady and more fully outlines the ways her relationship with her husband shaped both their lives.

In the biography, “Michelle Obama: A Life,” veteran journalist Peter Slevin portrays the first lady as a full partner in her husband’s political career and not simply a reluctant political spouse, as she is sometimes represented.

When she was in her late 20s and he in his early 30s, the couple began making important decisions together, selecting the next steps on their career paths. Slevin, a former Washington Post writer, notes that before they married and after Barack completed Harvard Law School, he moved in with Michelle, while her mother lived downstairs.

“Back in Chicago after graduation, Barack lived with Michelle on the top floor of the Euclid Avenue house, upstairs from Marian Robinson, as he studied for the Illinois Bar Exam,” Slevin writes. They soon married, which was important to Michelle.

A few years later, Barack Obama began his political career with a bid for the state legislature. According to Slevin, Michelle worked hard for his first election. She may have had misgivings about his choice of career, but she believed in him, the book says. That belief carried her through successive campaigns.

The 346-page book, one of the few in-depth biographies of the first African American first lady, is filled with history and context, including an exploration of Chicago’s political and cultural scene and where Michelle Obama’s parents and grandparents fit within the city’s social structure. Unlike more recent popular political tomes, which are often awash with Washington insider gossip, Slevin’s telling includes little about machinations within the White House.

It does have a few moments that may ruffle Michelle Obama, who closely guards the privacy of her mother and daughters. Slevin resurfaces an old interview with Marian Robinson from the public television show “Chicago Tonight,” which profiled Barack Obama in 2004 as he ran for the U.S. Senate. Asked how she felt about Obama’s biracial background, Robinson said with a laugh: “That didn’t concern me as much as had he been completely white. … I guess that I worry about races mixing because of the difficulty — not for, so much for prejudice or anything. It’s just very hard.”

Slevin notes that the concerns didn’t cause her to oppose the marriage. Robinson’s son Craig has said his mother was supportive of his marriage in 2006 to his wife, the former Kelly McCrum, who is white. “The reactions of my mother and Michelle were somewhere between ‘Phew!’ and ‘Hallelujah,’” Craig Robinson wrote in his book “A Game of Character.”

The first lady’s office had no immediate comment on the book, which largely depicts Michelle Obama in a favorable light while also looking closely at the role race played in shaping her worldview, particularly at Princeton and Harvard Law.

“To say that during her Princeton years she could not envision an African American president is like saying the sun rises and sets every day,” writes Slevin, who was not available for interviews about his book until close to its April 7 publication. “Michelle believed that there existed a separate ‘Black culture’ and ‘White culture.’”

The White House granted Slevin very little access, but he began reporting on the future first lady eight years ago while serving as Chicago bureau chief for The Washington Post. He is now an associate professor at Northwestern University’s Medill School of Journalism. For the book, he interviewed Michelle Obama’s mentors, staff members, former colleagues and relatives.

In the past, the first lady has not looked favorably on books about her. Upon the 2012 publication of “The Obamas” by Jodi Kantor of The New York Times, Obama told Gayle King, a journalist and friend: “I never read those books. … Who can write about how I feel? Who? What third person can tell me how I feel?”

The president has said his wife has begun working on her own memoir, to be published after his White House term ends.