Marrow

Robert Reed thinks big. A massive artifact (it is really too big to call a ship) is cruising through the galaxy on autopilot. No one knows what it really is, where it came from, or what its purpose is. However, humans and some other races colonize it anyway. Conflict inevitably develops and the disagreement in this story is a dozy, lasting over 5000 years. The ending seems rather inconclusive, but it is an interesting story nonetheless. (I suppose I will have to read the sequel.)