Erskine Childers 
The Riddle of the Sands [EPUB ebook] 

The Riddle of the Sands: A Record of Secret Service is an early example of the espionage novel, with a strong underlying theme of militarism. Carruthers, a minor official in the Foreign Office is contacted by an acquaintance, Davies, asking him to join in a yachting holiday in the German Frisian islands. Carruthers agrees, as his other plans for a holiday have fallen through. He arrives to find that Davies has a small sailing boat, not the comfortable crewed yacht that he expected.