I feel it is a bit lacking on the demonic side... It feels more like a really really really old book, from times when the world did not recognize life or death. The aura feels more like "ancient" than "demonic".
A fine exemplar of a spell book.
3/5 or 4/5, undecided yet
I don't feel the purple complimenting well with the rest of the icon. It feels a bit out of place... Maybe you could make the runes glow in purple-ish ?
The aura is a bit too faint an I'm not entirely sure if it would be visible in-game. I like it, but I don't think anybody would pay attention to it outside reviewing the art (e.g. during gameplay)