co-nun-drum (kon-'un-drum) [Origin lost.]... A pun or word-play depending on similarity of sound in words of different meaning ... A riddle the answer to which involves a pun; also, any puzzling question, problem, or statement ... A "what-d'ye-call-it".  From the Shorter Oxford English Dictionary

 

Like people and foreign movies, conundrums can be funny or serious, obvious or obscure, easy to understand or darn near impossible to figure out.  Unlike people, but still a bit like foreign movies, the conundrums in this book are provided with and without solutions.