What exactly is a "Light Novel"? I am only familiar with this term when I know about the anime.


Is this term only used in Japan? 


Sometimes I read light novels on the internet but I never see the book myself. How is a light novel different from a regular novel? Except for light novels being... light, are there any other differences?

And usually I see the cover done in a manga-style drawing:


Are light novels used exclusively for anime or manga adaptations? 
Are there any light novels that do not use manga-style drawings? 


I tried to search "Light novel cover" and the result is as expected:
What is a light novel?

A light novel is a style of Japanese novel targeting teenagers and young adults. These novels contain mostly illustrations in anime or manga style. They are usually published in bunkobon size (A6 – 105 x 148mm). Light novels are not very long. The length is comparable to a novella in US publishing terms.

Light novels are very popular in Japan as you can see in Japanese bookstores.



Where does the term come from and what does it mean?

The word “light novel” is actually not an English word. It is a wasei-eigo (literally translated “Japanese-made English”) which is a Japanese term formed from words in the English language.

The term is everywhere used where you read such novels. In Japan you will use the word raito noberu (sometimes also ranobe or rainobe as an abbreviation) which is the Japanese term of light novel.

In the western culture light novels are normally called Japanese Novella.

What is the difference between a novel and a light novel?

In short: Light Novels are usually shorter and they also contain few illustrations. In addition they are easier to read. This is particular because the text contains much simpler and easier to read modern kanji.

The illustrations are mostly at the beginning of capitals or when a new characters respectively a new place is described. On the picture below you see an example on how a light novel is build up. Left an image from the scene and to the right the text to read.



In typical light novels you will find mostly black and white illustrations. But today you also find many novels that include colored illustrations.



Why is a light novel styled like an anime or manga?

The reason because light novels are styled like anime or manga is because of their history and they are actually from Japan.


  Light novels are an evolution of pulp magazines. To please their
  audience, in the 1970s, most of the Japanese pulp magazines, which had
  already changed from the classic style to the popular anime style
  covers, began to put illustrations in the beginning of each story and
  included articles about popular movies, anime and video games.
  
  The narrative evolved to please the new generations and became fully
  illustrated with the popular style. The popular serials are printed in
  novels.
  
  In recent years, light novels' stories have been popular choices for
  adaptation into manga, anime, and live-action films, though in the
  case of the former two, usually only the first two novels are adapted.


Information from wikipedia, englishlightnovels, animanga.wikia, tvtropes.

Pictures from englishlightnovels, afrobonzai.unblog.