Traditionally, a werewolf in a story earned a book a spot on the shelf of the horror section of a bookstore. However, today there are many genres that include supernatural, potentially monstrous creatures that are not inherently cursed or evil. Categorizing a werewolf story is depends on the plot, not the supernatural creature.
For example, a werewolf murdering at night and the human struggling with the memories during the day would be categorized in the horror genre.
A story about werewolf falling in love and all the plot points revolving around their relationship would be categorized as a paranormal romance. This could be tricky because if the werewolf doesn’t have a happily ever after with their love interest and instead eats them, then we’re back to classifying the story as horror.
A werewolf detective or cop solving crimes is paranormal mystery. But, that’s not always the case. The genre would depend on whether the story is a hardboiled detective novel with a character who happens to be a werewolf or if the plot revolves more around the supernatural world at large with a character who happens to be a werewolf detective.
If you’re looking to go through a traditional publisher, let your agent and publishing house decide. If you’re an indie author looking to self-publish, do a little research and see which books with tropes, world building, and storyline are similar to yours. Finding the right genre is about finding the right audience. You don’t want to market your paranormal romance as a horror story or vice versa. Not unless you don’t mind a lot of angry reviews.
Hope you are all doing well. Happy writing!