Shelley It can definitely be read as a stand alone novel. Each book in the series focuses in a different character and doesn't require the reader to know all the previous characters.
Sarah I'm reading it right now and hadn't read any of the previous books, I believe I would be enjoying it more if I had. While it's a complete story there are lots of past characters showing up and past events that they were part of that I would be better able to understand if I had read the books that featured those characters and events. In my opinion you should read the books in series order.