I found it pretty easy to rank the nominees this year, in this order:

1. Ancillary Justice, by Anne Leckie
2. Evening’s Empires, by Paul J. McAuley
3. Ack-Ack Macaque, by Gareth L. Powell
4. God’s War, by Kameron Hurley
5. The Adjacent, by Christopher Priest

They were all very good, mind you, and I may well nominate them all for the Hugo.