Is there a preferred order to the novels (publication? internal timeline? other?)
This is one hell of a series. The Cormac books must be read first starting with Gridlinked. then drop back to start at the beginning of the timeline - the gabble can be read at the end as it references all the books and characters in the whole timeline. The Skinner is quite basic in the technologies Neal invented as he went through the writing process but the action sure makes up for that. Enjoy. Also try Peter F Hamilton's books if you like this series - though much more techfest than splatterpunk
Having read Gridlinked, I think that it is the one to start with for his Cormac novels, which also takes place in the polity universe. Amazon also says it is "Ian Cormac Book 1".
It now appears that The Owner series are also Polity books. So you could consider them prequels.
Never mind. Turns out the cover of "Departure" was a mockup of another Asher book and they forgot to remove the "Polity novel" part.