In what order should I read the lights novels of 'Tokyo Ghoul'?


I've recently started reading the manga of _Tokyo Ghoul_ and there were some
terms like Kakugan, Kagune etc. and some characters mentioned which are not
told earlier by the manga.

I then found that there are light novels of _Tokyo Ghoul_ which can help me
understand the backstory of characters more clearly and the terms too.

So, in which order should I read the novels? And should I read the manga
before or after reading the light novels?

