Irene Adler (the precognitive Mutant known as Destiny) collected images from her visions in the future into several volumes of books commonly referred to as "Destiny's Diaries" or "Destiny's Books". Rather than a detailed account of the future such as a novel, these books contained snapshots or glimpses of events that have not yet come to pass, and are often cryptic.
These diaries are what originally brought Mystique and Destiny together as Destiny approached Mystique sometime around 1900 seeking her assistance in understanding the visions written down in the diaries. The two would go on to become teammates and lovers. They were also a partial focus of the 2001 series: X-Treme X-Men, as the team led by Storm originally came together to search for the lost volumes of Destiny's diaries.
The diaries were eventually destroyed by Gambit, who burned them to ash before the X-Men or Marauders could read them.