I bought this book to help me while studying for RYA Day Skipper, but I'd recommend it not only to fellow sailors but anyone interested in charts and maps and how we know where we are on Earth. The first three chapters are a fascinating and important explanation of why we should treat maps and charts with caution as well as appreciation. The second part of the book is vital for any sailor as it lists the international standard for chart symbology, but goes much further than the dryness of Chart 5011, with explanations of how usage varies around the world. UK readers shouldn't worry that it was written for the US market, the author obviously has great respect for the British Admiralty charts and many examples use UK charts. Overall, highly recommended.