Book 11 in the Star Trek: Enterprise series.
"Over two hundred years ago, the life of one of Starfleet's earliest pioneers came to a tragic end, and Captain Jonathan Archer, the legendary commander of Earth's first warp-five starship, lost a close friend. Or so it seemed for many years. But with the passage of time, and the declassification of certain crucial files, the truth about that fateful day -- the day that Commander Charles "Trip" Tucker III didn't die -- could finally be revealed. Why did Starfleet feel it was necessary to rewrite history? And why only now can the truth be told?"