Mediator is a book series written by Meg Cabot. It was originally written under the Pseudonym Jenny Carroll.
It consists of 6 six books:
There will most likely be no more books in the series, although Meg Cabot is known to change her mind at the last moment. The books are about a 16 year old high schooler, Suze Simon. Suze is a 'Mediator', meaning she has the ability to talk to ghosts. She can also touch, hug, communicate, and kiss other ghosts.