Sorry if this is common knowledge, but I have 30 silouhette and harlequin romance books.  

I'd like to get rid of them all at once.  How would I go about that and still be within guidlines or rules?

You can run any kind of credit deal in the Bazaar (or in the specified post in the genre forum). You can send all for "x" credits. It's usual to have the person order the same number of books as credits you are asking, and then to include the remaining books as "free."