I'm in the process of uploading my most recent book to Amazon. It's number 3 in a series that will eventually be 5 books. Each of the books are pretty much stand alone - yes, there is some back story, but it's briefly mentioned and not that relevant to the current story.

So - should I advertise just the new book and mention that it's part of a series, or should I advertise the first book and the series and mention there's a new offering?

In general, how do you handle letting people know when there's a new book within a series?