The Demigod Diaries contains four new stories with character interviews, illustrations of Annabeth Chase, Percy Jackson, Jason Grace, Piper McLean, Leo Valdez, Luke Castellan and first ever seen pictures of Thalia Grace and Hal, a character that is introduced in the first story, puzzles, and a quiz.
It also includes a short story by Riordan's son, Haley Riordan, revolving around one of the demigods who fought for Kronos during the Second Titan War and survived the battle in Manhattan.