"Each book has been different and has been challenging in its own way to write"

This quote by Jean M. Auel speaks to the special challenges that featured writing a book. Each book is different and needs its own technique and design. Writing a book is an uphill struggle, and each book provides its own set of difficulties. Auel is most likely referring to the trouble of creating a story that is both engaging and original. It is not easy to come up with a story that is both fascinating and special, and this is something that Auel has actually had to confront with each book she has actually written. Composing a book is a hard process, and Auel is acknowledging the unique challenges that featured each book.