Bungo Stray Dogs is both. It began as a light novel and then was transformed into a manga. The light novel provides detailed storytelling, while the manga brings the characters and scenes to life visually.
Well, you could say there are hints of love here and there. But it's not a conventional love story. The series is primarily known for its action and supernatural elements with love being a secondary aspect.
One of the main themes is the exploration of special abilities. Each character has their own unique ability, which leads to various power struggles and cooperation. Another theme is the concept of good and evil. The characters are not simply divided into good or bad, but are complex individuals with different motives and backstories.
The number of Bungo Stray Dogs light novels is not fixed. It keeps increasing as new ones are published. You can check the latest information on official bookstores or the publisher's website.