John Buchan 
Heroes of John Buchan – Richard Hannay in ‘The Thirty-Nine Steps’ – Edward Leith in ‘Sick Heart River’ – Sandy Arbuthnot in ‘The Courts of the Morning’ [EPUB ebook] 

John Buchan may hold the title of the man who invented spy adventure, bringing Richard Hannay fully formed to readers in the early 19th century. Hannay is just one of his masterful creations, Edward Leithen and Sandy Arbuthnot would follow the Hannay novels and bring their own unique adventures to millions of enthralled readers.