I'm not sure specifically as I haven't read it in detail. But generally, it might be about the appearance of a final boss in a rather unexpected or 'wild' way in the story world of the light novel.
There's no way to know for sure just from the title if it's popular. Popularity depends on a lot of factors such as the writing style, the marketing, and the overall story concept. Just because it has an interesting - sounding title doesn't mean it has a large following. However, if it has been well - received by readers who like this type of story, it could potentially be quite popular within that niche.
Well, in many novels, the appearance of the last boss often represents the climax of the story. It's the ultimate challenge for the protagonist. For example, in some fantasy novels, the last boss might be a powerful dark wizard or a terrifying monster. Its appearance forces the hero to use all their skills and knowledge they've gained throughout the story.
Since I don't know the exact details of 'a wild last boss appeared novel', it could potentially revolve around a gaming - like scenario within the story. For example, the characters could be in a virtual or real - life adventure where they encounter this unexpected and extremely difficult 'last boss'. It might explore themes like courage, strategy, and the growth of the characters as they strive to overcome this final obstacle.
In this novel, a wild last boss shows up, throwing the normal order into disarray. The story follows the characters' attempts to deal with this powerful and unpredictable threat, with lots of action and adventure along the way.
One of the main themes is the struggle between good and evil. The last boss represents a great evil that the heroes must overcome. But there's also the theme of the underdog. Sometimes the heroes seem like they have no chance against the all - powerful last boss. Also, the theme of discovery is present, as the characters learn more about the last boss as the story progresses.