The Animorphs Chronicles is a series of 4 books written by K. A. Applegate alongside the main series as a companion collection to detail the backstories of characters introduced in the series, and help explain and expand upon concepts that were briefly defined in the series, but, as the series is told from a human point of view, were limited in terms of what could only be explained through in-story dialogue. Four Chronicles books were published; The Andalite Chronicles in 1997, The Hork-Bajir Chronicles in 1998, Visser in 1999 (the only Chronicles book not to feature the words "the" or "chronicles" in its title), and The Ellimist Chronicles in 2000. The Chronicles books are unique amongst the Animorphs continuity in that they are told from previously largely unfamiliar aliens' perspectives, and not from one of the 5 main human points of view (nor Ax's, after being introduced), bar the beginning and end of The Hork-Bajir Chronicles, which are narrated by Tobias. All four books feature artwork by Romas Kukalis on their covers. Source: Wikipedia (en)