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.
To open a manga cafe, you have to have a good collection of manga. Also, create a cozy and inviting atmosphere. Offer comfortable seating and maybe some snacks and drinks. And don't forget to market your cafe well through social media and local promotions.
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.
Definitely not. Having sex at a manga cafe is inappropriate and against the rules and purpose of such establishments. It's a place for enjoying manga and having a quiet time.