The historian Annette Gordon-Reed’s “On Juneteenth” is an unexpected book. She’s best known for her work on Thomas Jefferson and Sally Hemings, the enslaved woman with whom Jefferson had multiple children — a once controversial thesis that’s now accepted as historical fact in large part because of Gordon-Reed’s scholarship. She has written before about the need for historians to maintain a certain distance from the people they write about, to see “the complexity and contradictions” that might otherwise get crushed in an overzealous embrace.

In “On Juneteenth,” Gordon-Reed identifies quite closely with her subject — and only a sliver of the book is directly about Juneteenth itself. But if this book is a departure for her, it’s still guided by the humane skepticism that has animated her previous work. In a series of short, moving essays, she explores “the long road” to June 19, 1865, when Maj. Gen. Gordon Granger announced the end of legalized slavery in Texas, the state where Gordon-Reed was born and raised.

Her family’s Texas roots run deep, to the 1820s on her mother’s side and at least as far back as the 1860s on her father’s side. She remembers Juneteenth celebrations from her childhood, drinking red soda and setting off firecrackers that her grandfather bought. The history they were commemorating still felt close, with slavery “just a blink of an eye away from the years my grandparents and their friends were born.” When she heard that people outside of Texas were starting to celebrate the holiday, she confesses that she “was initially annoyed,” feeling a “twinge of possessiveness” that she chalks up to “the habit of seeing my home state, and the people who reside there, as special.”

And Texas is special, she says — though not exactly in the ways that it’s usually made out to be. Yes, it’s big, not just geographically but also historically: “No other state brings together so many disparate and defining characteristics all in one — a state that shares a border with a foreign nation, a state with a long history of disputes between Europeans and an Indigenous population and between Anglo-Europeans and people of Spanish origin, a state that had existed as an independent nation, that had plantation-based slavery and legalized Jim Crow.”