wings (or the ability to move through the air naturally) are what humans do not have and always kinda wanted...and that's why mythological versions of (both men and) women were imagined to achieve this impossible, as a transposition of an ideal. in relation to villains (like witches), flight becomes almost a weapon (the creature even flies, the thing man can't do, fear it more), to inspire a bigger threat. the last thing to mention would be that sometimes it was not the fantasy of flight which inspired humans to give a creature wings, but it was a logical assumption, based on what the creature is supposed to represent, do, or the place it inhabits (it lives high up in the mountain cliffs - it must fly to get there; it comes from the sky/heavens - it flies somehow or has wings; it's a fairy - like nature's many almost invisible insects, it has wings; it can reach any room in any house, even on a top floor - it has wings or levitates spirit-like; it's supposed to represent the merge of all elements in one creature, fire, water, air, earth - air can be represented by flight or having the wings of a bird; it's supposed to represent another creature which already has wings or flies somehow - she's like an angel/divine, she also has wings, she's the protector of dragons/swans/something, she also has wings, she's like other special creatures which have wings already, she also has wings; etc).
the book provides a lot of information, but i felt it also veered a lot from these three very simple ideas behind monsters and enhanced people which have the power of flight. additionally, it also just explains various mythological ideas a bit too much beyond any relevant point to the theme of the book, and, in relation to some of the creatures, some things also seemed a bit misinterpreted at times.
still, the book appears to be the result of a lot of work, which is why i tried not to tax it too much.
the title is not really a good fit based on the content, the book evolves to be less and less about flight as it progresses, more here and there.