Gray's Sports Almanac was a catalog of sports scores from 1950 to 2000, originally purchased by Marty McFly during his visit to the year 2015 but stolen by the 2015 version of Biff Tannen. Tannen won his first million betting on a horse race in 1958 and through his actions of that timeline, was responsible for the creation of the hellish Biffhorrific Hill Valley. (Back to the Future Part II)
Shortly after purchasing the book, Marty McFly confided to Dr. Emmett Brown that he intended to use it to win some money back in 1985. Horrified, Brown stated that he did not invent the time machine for financial gain, and after an argument ensued, Brown tossed the book into the garbage.
However, Biff Tannen overheard this conversation and stole both the book and the DeLorean time machine and took the text back to his past self in 1955. By 1985 of this altered timeline, Biff was one of the most powerful men of 20th century America. (Back to the Future Part II)
This timeline was thought to have been erased by the temporal incursion of Emmett Brown and Marty McFly, but it continued to exist as part of the multiverse. Biff used the book as one of his multiple sources of wealth, though by that reality's 1985, he had very little need for it. (Star Trek: Voyager - Dark Realm)