JFK’S LAST HUNDRED DAYS: The Transformation of a Man and the Emergence of a Great President. By Thurston Clarke. Penguin. 448 pages. $29.95.

For a blunt-titled book with a tragic conclusion that every reader knows from the start, Thurston Clarke’s “JFK’s Last Hundred Days” manages to surprise and even occasionally to delight.

This book is about life, a quick-pulsed three months of life, before it’s about death. It’s about forward movement and daily accomplishments, often history-making ones, before it’s about lost opportunities and, as the Israeli statesman Abba Eban characterized the assassination of the young president in his prime, “one of the most authentically tragic events in the history of nations.”

It’s worth noting that among these 100 days were some that John F. Kennedy himself called his happiest. The story line of these days takes the reader from early August 1963 through his death on Nov. 22. The book has the feel of a wide-ranging diary, each chapter focusing on a successive week or even a single day. It details Kennedy’s personal dealings — playing with his young children, John and Caroline, in the Oval Office, for example, or singing sentimental songs at the family compound in Hyannis Port, Mass. — as well as his political maneuverings and presidential actions. At times, the events are laid out hour by hour, but never tediously.

This was a time in which civil rights activism was rising toward a crest. We see Kennedy conferring with black leaders and, in one testy White House meeting, with the white leadership of Birmingham, Ala., amid deadly violence there. As the March on Washington plays out at the Lincoln Memorial, we see the president listening at an open White House window with a black doorman as the throng sings “We Shall Overcome.”

Kennedy skeptics may be dubious of some of its implied or stated projections. Would the Civil Rights Act have passed if he hadn’t been killed? Would he have found the way out of Vietnam that he sought, or an approach to Russia and China that could have hastened the Cold War’s end?

Small, telling details about JFK get hoovered up along with the big things, such as policy debates recorded by secretly installed Oval Office microphones, to create immediacy and surprise. When the always restless Kennedy doodles during dull meetings, Clarke’s descriptions of what he draws give a glimpse into the president’s mind.