It is good that the writers are honouring the tradition of Yoga by linking the asanas to the myths. I also liked the fact that they recognise the links between the myths, asana practice and the development of personal qualities like loyalty, faith, generosity and persistence. If you are looking for a children's book, or if you just want an easy read on the myths, or perhaps (if you are a yoga teacher) an easy reference point for stories to mention in class, then this could be the book for you.
However, if you want more, if you really want to delve into the meanings of the asanas, then you need to know how to do it. For this, there are much better books on the market.
Swami Sivananda Radha's 'Hatha Yoga; the Hidden Language' brings the ancient yoga myths and the symbolism of nature together with the asanas in a more helpful way. It helps you to move to a deeper level, to take the asanas as reflective and meditation postures, observe how each one affects the mind and the body, make connections between what you are experiencing as you do your asana practice and your daily life. It also helps you to move towards deeper understanding, making your own discoveries.
Another book worth mentioning is Swami Lalitanada's 'Inner Life of Asanas'. This is a more personal illustration of working with asanas. She takes many of the poses covered in 'Myths of the Asanas' and explores insights she has had from her practice. Swami Laltananda provides instruction and takes yogic themes (such as developing awareness, exercising choice and moving towards union) to demonstrate by example, how to bring the teachings and our experiences together in our practice.