Animorphs Chronicles
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 . 
<triplet> Animorphs Chronicles <subj> K. A. Applegate <obj> author