John Buchan 
The Thirty-Nine Steps [EPUB ebook] 

The Thirty-Nine Steps by John Buchan, a thriller and an adventure, is a fascinating read set in the times of impending World War I. Adventurer Richard Hannay, just returned from South Africa, is utterly bored with London-life until he is approached by a mysterious American, who warns him of an assassination plot that could completely disrupt the delicate political balance of Europe. Initially skeptical, Hannay nonetheless hides the man in his home. But the plot takes an interesting twist, as one day, Hannay returns home to find the man murdered. An apparent suspect, Hannay flees to his native place in Scotland, pursued by both the police and a cunning and ruthless enemy. His life and the security of Britan are under jeopardy, and everything rests on the answer to a baffling mystery: what are the 'thirty-nine steps?'