John Townsend 
Operation Code-Cracker [PDF ebook] 

Code-loving Max is unexpectedly recruited to spy on his friend”s uncle, a suspected terrorist. But nothing is quite as it seems in this new world of espionage, double-crosses, kidnaps and car chases – and in the end, it may be Max”s skill with word puzzles that saves the day. A thrilling, non-stop adventure packed with puzzles for the reader to solve.