For the record I am a huge fan of this series.
Spice and Wolf is about the relationship between Lawrence and Holo, how they interact, the challenges facing them, the banter between them, their growing fondness of each other, every aspect that makes them a perfect couple.
Upon their chance meeting, they travel together with Holo making a request of him to take him to the north, along the way as Lawrence is a peddler, he travels from town to town selling his goods, meeting new people, getting into situations alongside Holo and generally having fun with his companion.
They both however get involved in a situation that lasts the entirity of this series, and to be honest its very well done, very exciting and very much likable.
I would say this series will appeal to both males and females looking for something different. There is next to no fanservice(After episode 2, the first 2 episodes have some fanservice moments), some scenes of violence, and that's it really.