I can second the Ninefox Gambit. It's a strange science fantasy (like Star Wars) which revolves around using mathematics and calendars to drive exotic machinery and technology.

I'll be honest, I found Ancillary Justice a little boring since the characters aren't very complex. It's interesting in that it's from an A.I.'s perspective involving many simultaneous inputs (multiple sensors, people, etc).

Also, I have to give the obligatory fiction recommendation for Red Rising. That trilogy is like the roman empire in space, but the characters are what really make it.