This book has been described as 'a fable'. It is very easy reading and once I started it, I could not put it down. I read it over the course of 1 day! I think that there are clues in the title and in the jacket design, so I'm just going to repeat here what the publishers say inside the book jacket:-
'The story of The Boy in the Striped Pyjamas is very difficult to describe. Usually we give some clues about the book on the jacket, but in this case, we think that would spoil the reading of the book. We think it is important that you start to read without knowing what it is about.
If you do start to read this book, you will go on a journey with a nine-year-old boy called Bruno. (Though this isn't a book for nine-year-olds.) And sooner or later you will arrive with Bruno at a fence.
Fences like this exist all over the world. We hope you never have to encounter such a fence.'