Ysabel is the story of a young protagonist who finds himself involved in a spiritual battle by way of psychic powers and the ability to communicate with the dead. The story portrayed is part of the Roman conquest of France, and the unfairness that each suitor feels in regard to their love for Ysabel.
There is an interpretation available on that point: unfairness. Unfairness leaves Ned uniquely burdened to understand the story, and burdened by the bitterness of both sides of the conflict in which he finds himself. His quest is ultimately tied to the competition of the suitors. The novel is showing Ned as part of an ancient quest for love and joy, depicted through the allegory of a love-triangle.
However, the really important part is that Ned's motivation is not the same as the suitors. The suitors have condemned themselves to an afterlife of longing and striving, because they made the lover into an object to be obtained, but Ned reaches his goal, because he is motivated to save Melanie from the spirit of the objectified lover. Because he is motivated by virtue, he finds himself able to finally summit the mountain that had left him sick and confused.
