This listing is for a Box Set of four Animorphs books.  They are from 1997.  The books are #13 - The Change, #14 - The Unknown, #15 - The Escape, and #16 - The Warning.   Book #15 has a bit more wear to the cover than the other books.  I will have other Animorphs books listed.  I will gladly combine shipping.  Please e-mail any questions.