The 39 Steps by John Buchan (1915)

Alfred Hitchcock was well known for adapting a book to his liking.  He was not one to stick too closely to the original, so if you think that having seen the movie you know what the book is about, you are both right and wrong.  The main character is the same, and the same general principle is there, that there is a spy afoot and something needs to be done to prevent the spy from passing on their secrets.  It does largely take place in Scotland and some of the people who help our hero are the same in the book and the movie, but that is about where the overlap stops.


The book is set in the days before WWI.  England is quite uneasy about Germany and what will happen next.  Much effort had been devoted to maintaining their colonies and that left them unexpectedly vulnerable.  The colonies may have been a source of significant wealth in the 19th century but they led to a lot of trouble in the 20th century and this book was written right on the brink of that change.  Much like Downton Abbey, it represents a tide change in Britain and this book is a window into what it was like before all that changed.  With espionage thrown in to make it interesting.