I was intrigued by the title and even more so by the book. I am not a seasoned user of the London Underground but on the couple of times of year I do use it I'm always plagued by questions (one of the main ones being 'why?'). Rosemary Kind answered all my questions and many, many more - but even better, she made me laugh at loud at least once per page and she actually made me look forward to my next visit to London. (And my favourite game, 'Mornington Cresent' got a mention - hurray! Kind's explanation of the rules was phenomenal...)
Highly recommended!