I must start by saying that I have an innate prejudice against books written entirely in the form of letters. However, this novel went a long way towards curing me of this.
The Guernsey Literary and Potato Peel Pie Society is set just after World War 2, when the German occupation of Guernsey in the Channel Islands had only recently ended. The central character is a writer, Juliet Ashton, who begins a correspondence with the members of the eponymous society. They are a group of disparate individuals who met regularly during the occupation to read and discuss books, keep their spirits up, and provide mutual support (and as they tell their stories, it becomes clear that the support given was very much practical as well as emotional).
I found reading this book a bit like listening to a radio play. Each of the letter-writers has his or her own distinctive voice, and gradually you get to know and understand them better, both through seeing what they write themselves and what others write about them. Although I do still have some reservations about novels written entirely in this form, I have to admit it works well at showing readers the characters from different perspectives and bringing them more vividly to life.
The book is perhaps a little slow in the beginning, as we read letters sent between Juliet and her publisher and other people in her life such as her friend Sophie. As the correspondence with members of the society gets into its stride, however, the book becomes much more gripping. There is a lot of presumably well-researched information about what life was like in the Channel Islands during the German occupation, and it really does bring this lesser-known aspect of WW2 into vivid focus. To the author's credit she pulls no punches about the worst aspects of life at that time, both in Guernsey itself and in the Nazi concentration camps. Some readers might find certain scenes described in the book quite disturbing.
It does, however, have a happy ending. A harsh critic might say that it has a touch of the Mills & Boon about it as Juliet finally finds true love, but of course I would say no such thing!
In summary, then, this is an entertaining and at times moving novel, with a fascinating background.
Edited to add: I have just discovered that Ms Shaffer passed away shortly before this book was published. I'm very sad to hear this, and sorry that there will be no more books from her pen.