(Updated June 26) More than 20 candidates have announced a bid for the presidency, and many of them will lay out their policy positions on Wednesday and Thursday during the first Democratic presidential debate. Often, politicians release books pegged to their announcements to drive interest and give voters a chance to get to know them. Here is a guide to some of those books, which can provide insight into the candidates’ priorities and worldview.

Senator Michael Bennet, Democrat of Colorado

“The Land of Flickering Lights: Restoring America in an Age of Broken Politics” (2019)

This book does not lay out specific policy proposals, but rather “reads like a sweeping diagnosis of the nation’s political ills,” which include, in Bennet’s view, “a desperate aversion to bipartisan discussion and a crippling reliance on short-term thinking,” wrote our reviewer.

Joseph R. Biden Jr., former vice president

“Promise Me, Dad: A Year of Hope, Hardship and Purpose” (2017)

Though Biden has a three-book deal with Flatiron, his last book was this memoir of his son Beau’s last year of life. (He died in 2015.) “What’s most remarkable about this book,” wrote our reviewer, is that it gives us “full visibility into the agony and strangeness” of caring for and mourning his son while fulfilling his duties as vice president. But it’s also a political book, she added, “one in which Biden touts his accomplishments and makes frequent forays into the wetlands of foreign and domestic policy.”

Senator Cory Booker, Democrat of New Jersey

“United: Thoughts on Finding Common Ground and Advancing the Common Good” (2016)

Booker, raised in New Jersey and a former mayor of Newark, argues in this book that American politics should be reoriented around compassion and solidarity. He told The Times that writing it was “far, far more difficult than I had expected,” and he cried when writing about the toughest parts of his life, including the death of a mentor.