The most important thing to know about this book is that Gudrid is mentioned in the Sagas. What sagas, you may ask. The Icelandic Sagas, long held in Iceland to be actual history and only recently determined by archaeologists to be more than legend.
This book uses Gudrid as a framework to study the Sagas and the world they describe. Her life, as told in the sagas, serves as the background for modern scientific studies of a past forgotten but important for us to understand where we came from.
The Sagas, as a side piece of information, were studied by Tolkien and other fantasy epic writers, and have a great influence on what we think of as fantasy.