Light Novels are a book medium from Japan. They are shorter than novels, hence the name, but are regularly released in multiple volumes. Consequently, while each individual book is fairly short, the entire series can be quite long.
Light Novels are a fairly popular medium in Japan, and the medium has started spreading internationally, through the overall spread of Japanese culture.

• AniList
  • AniList contains entries on Light Novels. Although, they are categorized under manga, which makes management unusually difficult.
• Novel Updates
  • The closest thing to a database for Light Novels. It is mostly focused around fan translation however.