The solution came to me through quite a bit of thumbnailing and the main two things that I did were -
eliminating all the characters from the cover, because it is reasonably hard to tell, which ones out of all are the main, and trying to transcend the general mood of the book through the patterned shapes and the colors of the cover, as well as the materials, which are chosen to give a certain feel to the novel.
The book would be made in leather cover with a tapestry illustration pasted into it. The main motif is the Ring and the Eye of Sauron seen through Galadriel's mirror at Lothlorien, the mirror, which shows the Past, the Present, the Future, and That, which Would Never Happen. This to me signifies the intertwining of the "Dark world", "evil" side of the book with it's lightest, hopeful, beautiful side. The complexity of the patterns translates the complexity of the story and the roots are like the many lines of the plot intertwining in one single tapestry.
Please tell me what you think, your comments are really precious to me as that is the only way I can know for sure what works and what doesn't.