There is but it hasn't been published yet
It already has.
the fourth book is coming out on augest 23rd and is called torn
As of now, the Night World series by LJ Smith consists of nine books. There is no fourth book known to exist in the series.
Yes, there will be a fourth Ghostgirl book coming out next November.
# # # # # #
Yes, it's called Dark Angel. Yes it is. Well kinda anyway. Dark Angel is the fourth story in the second book. The fourth book should come out soon and it's called Strange Fate.
Rapture is the name for the forth book
The 4th book is coming out in September 2010, It is called: This isn't what it looks like
21st of June
never sorry
The next book is number 10 and they cant find a date. Sorry I could not help.
It's quite simple there is no fourth book (its just a trilogy)