Here is some inspiration, check it out:
Anja Uhren 1
Anja Uhren 2
I took pictures of the process, so, if you want, you can make yourself one, too.
It is actually pretty simple. First you strip off the transparent foil and the bookcover, if you like. In this case it came off with the foil. In case it stays on you can probably use it on the book cover as a foundation for your own artwork. Remove paper and foil from the insides of the cover, too. Then Gesso everything to prepare the book pages for further work. I am using Guardi Gesso. I just discovered Gesso for me, never really heard of it before. Checanty recommended it to me, and it is actually pretty useful and not that expensive.
I gessoed some pages on the inside and started a little test-sketch with pencils. Then I worked over it with watercolours, gouache and graphit-powder mixed with water. After that I went over it with some transparent gel to fixate it and prepare the surface for my acrylic markers. These markers cover well and provide a nice sharp edge.