Katherine Applegate, who also writes as K. A. Applegate, has authored more than one hundred books. While her publications include romances for the Harlequin line, she has aimed most of her writing at middle-grade readers, penning some titles for the popular "Sweet Valley Twins" series and authoring several books featuring Disney characters. Applegate's most successful venture in juvenile fiction, however, has been her creation of the "Animorphs" series. These books, about young adolescents given the power by aliens to "morph" themselves into various animals, have rivaled R. L. Stine's "Goosebumps" series in popularity.

Applegate has completed many titles either in the "Animorphs" series or related to it, such as the "Megamorphs" series wherein the characters take turns narrating chapters, and the "choose-your-own-adventure" "Alternamorphs" series. Writing in Horn Book, Christine Heppermann attributed the series' success to this: "Readers can take what they want from it--the animal info or the...