John Buchan 
Greenmantle [PDF ebook] 

British writer John Buchan’s Greenmantle is the second of five adventure novels to star Richard Hannay, a man with a remarkable knack for getting out of sticky situations, and indeed getting into them in the first place. During the First World War, amid news of an uprising in the the Islamic world, Hannay must make the dangerous journey through enemy territory into Constantinople, in order to foil a German plot to use religion to dominate the war. Greenmantle follows on from Buchan’s The Thirty-Nine Steps.