Encouraged by the success of the television series Downton Abbey, the author of the book decided to write about the life of Lady Almina (known as the Countess of Carnavon) and her family, as they are the inspiration behind Cora Crawley and other characters in the show. While Dowton is only loosely based on their lives, the majority of the book discusses how Highclere Castle was indeed turned into a hospital during the Great War and how Lady Almina became an exemplary nurse.
As a fan of the show and a WWI buff, I was happy to find this book in my cousin's husband's library. It was a quick, easy read that did not impress me very much. I do not regret reading it because it is always good to know the truth behind fiction and that such hospitals were created during the war, but the writing style was very blend and their lives busy but fairly uncontroversial.
If you're a fan of the show and have some spare time, I'd say "why not?" If not, there's no point for you to read this.