The Wall by John Lanchester
The Wall is a neat, disquieting, elegant book that deserves to be read. It creates the fantasy of a walled-off Britain, and reveals it to be a nightmare. Kavanagh begins his time patrolling the Wall. If he's lucky, if nothing goes wrong, he only has to do two years of this. The best thing that can happen is that he survives and gets off the Wall and will never have to spend another day of his life anywhere near it. But what if something did happen - if the Others came, if he had to fight for his life. Thrilling and heartbreaking, The Wall is about a troubled world you will recognise as your own - and about what might be found when all is lost.