This sourcebook was bundled with the adventure "Return to Axanar".
From the book description:
"[This book] details The Four Years War. Essays by Federation experts on Axanar, the major battles, and the political, social, and economic factors are indluded."
From inside the book:
"THE FOUR YEARS WAR
A Concise Compilation of Library Information on the Conflict Between the United Federation of Planets and the Klingon Empire, stardates 1/9409 through 1/9806."
A supplement for use with STAR TREK: The Role Playing Game."