Spice and Wolf started as a novel. Later, it was adapted into a manga. So, it's both, but it originated as a novel. The novel provides the base story that the manga builds upon.
Start with basic shapes to form the wolf's body. Pay attention to the proportions and the distinctive features like the ears and tail. Sketch lightly at first to make corrections easily.
The ending of Spice and Wolf manga is bittersweet. Holo and Lawrence's relationship reaches a significant point, but it leaves some room for interpretation.