Giving Form to the Formless
I give birth to Father (Heaven) on his (own) head [Agni]; my womb is in the waters, in the sea.
Thence I spread forth across all worlds, and yonder heaven with its height I touch.
I, just like the wind, blow forth, grasping at all worlds,
beyond heaven, beyond this earth here—of such size in my greatness
have I come into being.
— Devi Sukta, Rigveda 10.125.3 – 10.125.8
Devdutt explains the origin of shiva with artefact of indus-valley civilization and stories of past.Shiva has pre-Vedic tribal roots, having "his origins in primitive tribes, signs and symbols...Of several Indus valley seals that show animals, one seal that has attracted attention shows a large central figure, either horned or wearing a horned headdress and possibly ithyphallic,seated in a posture reminiscent of the Lotus position, surrounded by animals. This figure was named by early excavators of Mohenjo-daro as Pashupati (Lord of Animals, Sanskrit paśupati),an epithet of the later Hindu deities Shiva and Rudra..Sir John Marshall and others suggested that this figure is a prototype of Shiva, with three faces, seated in a "yoga posture" with the knees out and feet joined (wikipedia)
The book relates lord shiva with many sacred symbols.The main theme behind Shiva's life is elaborated with idea of sat chitta Ananda.You can explore a whole new world to realize the effort that are given from Gods and Goddesses to transform a yogi into the household.So surely it's a balanced book with lots of philosophy, mythology and spiritual ideas.