Kodansha's Furigana Japanese-English Dic

Browsing through the pages of Kodansha's Furigana Japanese-English Dictionary, you will notice something different: none of the Japanese entry words appearing in this book have been romanized. Some people may be surprised by this feature, especially in that the book is seen as suitable for even absolute beginners. Others (particularly the Japanese-language instructors who pointed out the need for such a publication) will be delighted to find that a full-fledged furigana Japanese-English dictionary is finally available. What is furigana and why is it so important?