This image is perhaps almost to dark in its representation, although there is certainly a dark thread running through the novel. However this simplistic representation of smoke and mirrors might be better aimed at the more mature spectrum of a YA readership. However that said I think the blue smoke could work well with the castle turrets perhaps edging out of the top. with the text layers then on top and centered.
READ about: THREE RIVERS DEEP book series on FACEBOOK @ https://www.facebook.com/threeriversdeepbooks?ref=aymt_homepage_panel ***A two-souled girl begins a journey of self-discovery... (pic source: http://strangelandevil.tumblr.com/post/132607401365/imickeyd-mark-avgust-black-nature Mark Avgust - black nature)