Kent State: What Happened and Why by James Michener (1971) is still the definitive account of May 4, 1970. Michener spent months in Kent interviewing students, faculty, National Guard members, and residents in the aftermath of the shootings. The book is long and thorough — sometimes slow — but it captures the full complexity of how a student protest escalated to a killing. Reading it before you visit the memorial gives you a completely different experience of standing in that parking lot.
The Vietnam War context matters too, and A Rumor of War by Philip Caputo (1977) remains one of the best memoirs of fighting there. Caputo served as a Marine officer in 1965–66 and the book is honest about how the war changed the men who fought it. Understanding what the students at Kent State were protesting — and why it felt urgent enough to march over — requires understanding what the war actually looked like to the people in it.
The Days of Rage by Bryan Burrough (2015) covers the broader arc of 1970s American radicalism, including the Weather Underground and the antiwar movement's violent fringe. It provides context for why the political climate in May 1970 felt, to everyone involved, like a moment of genuine crisis rather than an ordinary protest.
Crooked River Burning by Mark Winegardner (2001) is a novel set in Cleveland from the 1940s through the 1960s — not Kent specifically, but the northeast Ohio landscape and the particular texture of midcentury industrial Ohio come through vividly. Good reading for anyone spending time in the region.