Dr Russell Buchan’s new book Cyber Espionage and International Law offers a timely and thorough examination of the application of existing public international law doctrines to the practice of peacetime interstate cyber intelligence operations. In doing so the book carefully walks readers through a complex wilderness of mirrors, a landscape populated by spies, saboteurs, hackers, and surveillance intermediaries. Grounding his work is a profound understanding of the foundational principles of international law, and Buchan does a superb job both introducing them to readers and making the case for their unique operation in addressing the contemporary challenges posed by new surveillance technologies. Since the dawn of the printing press there have only been a handful of books ever written on the law of nations as it applies to the second oldest profession. Buchan’s work thus offers a valuable contribution to what is an emerging legal debate seeking to promote greater clarity around international rules on espionage.