A light novel is simply a thin novel without a thousand pages that tells the story of an anime. Usually anime is based off them if it's not a manga first. Some examples of the novels preceeding the anime are:

Shakugan No Shana
The Melancholy of Suzumiya Haruhi
Full Metal Panic
Spice and Wolf
The Slayers

There are a looooot more. I've started collecting the Haruhi ones in English AND I LOVE THEM!! Highly recommend them!! KYON IS SOOOO HILARIOUS. XD I bought the first one of Shana but haven't read it yet. Anyway, it feels great to read an actual book instead of manga ALL the time. :eyespin: Not that there's anything wrong with manga but I needed to enhance my vocabulary. :meh:

A while ago, I started writing Full Moon (manga) in novel form...XD; I wonder if I should continue. It was kinda fun. :tongue:

There are light novels in Thailand too. :) If I don't misunderstand, some popular series're also copyright in Thai.

Shakugan No Shana
The Melancholy of Suzumiya Haruhi
Kanokon
etc. There're more but they are not yet to be anime.

I'm reading Shana vol.7. It isn't same as anime but not bad for novel.