-- (later) -->
I started from step 2 and tried to apply steps 3 and 4 with the geometry I try to achieve (rounded cover, with slight bumps at each edge, due to the seams -- see profile shape on the left).
I may still have
the second version try to fix some remaining errors with step 4. I also kept my original colour for the paper (I try to make the book look old, with yellow-ish paper), but if you switched to white-and-cyan for a purpose, I'd be curious to know.
As for step 5, I must admit that I don't get the process through which you picked those pink/cyan tints you have used ... But seen at 1x, you managed to have something much convincing for the shadow on the paper than what I ever got. If there's a rationale / tutorial about this, I'm curious as well.
meanwhile, I took a quite opposite approach to colour harmony by making a miniature of the scene and try to "zoom & refine" it progressively. So far, it brings this:
<-new test | for ref->
It's easier for me to experiment other tints ... although I still stay much more "conventional" compared to the color revamp you made. edit: more book references