The Riddle of the Sands annotated

Considered the first proper spy novel, Riddle of the Sands is about two blokes floating about in a boat who suspect Germany is plotting an invasion from the Frisian Islands. The story may be fiction, but Childers knew both sailing and the Frisian Islands inside-out, and wrote non-fiction books and articles about how Britain needed to update its military strategy in the Baltic. It was Riddle of the Sands that made an impact, though.