The Discworld Diaries are a series of themed diaries based on the Discworld novels by Terry Pratchett. Each one (except the 2008 diary) is based on an Ankh-Morpork institution, and has an opening section containing information about that institution written by Pratchett and Stephen Briggs.
The diaries feature a great deal of background information, far more than could reasonably be put into the novels. However, some of this occasionally finds its way into the series proper - the concept of female assassins and the character of Miss Alice Band were two notable ideas that first appeared in the Assassins' Guild Yearbook.
Discworld's Unseen University Diary: 1998; the cover art features the character Death, possibly the character who appeared in the greatest number of Discworld novels.
Discworld's Ankh-Morpork City Watch Diary 1999: 1999; the cover art features the character Commander Samuel Vimes of the Watch, His Grace the Duke of Ankh, in his beloved street uniform, in other words, battered Watchman armor.
Discworld Assassins' Guild Yearbook and Diary 2000: 2000; the cover art features the character Lord Downey, the Assassins' Guild leader, with his specialty peppermint (rumored poisoned).
Discworld Fools' Guild Yearbook and Diary 2001: 2001; the cover art features Dr Whiteface, the Fools' Guild leader, bursting through a paper hoop.
Discworld Thieves' Guild Yearbook and Diary 2002: 2002; the cover art......