This is egregious.
Look at the original art (left.) The Harper Collins book cover is on the right.
Wow. Other than the fact that the HC cover is less artistically interesting both in composition and detail, and the color and light are all wrong, it's a revoltingly close copy.
Did they know? Is this just a coincidence?
Heck, no. HC contacted Nathalia Suellen (the artist) to buy this exact piece of art for this exact book. She wouldn't sell it to them because she had already sold it to someone else for a book cover.
So they copied it.
Right down to the bird.
Read her story at http://blog.ladysymphonia.com/