Oh, that's a tough one.
War seems to be a recurring theme throughout my works, and in particular the impact is has on people. I'm a very character inspired writer; I find people, and their emotions and motivations far more interesting. I guess war (or any large scale conflict) makes character-based works easier. Idk.
Almost paradoxically though, I do like playing with positive-future sci-fi as well. I like the idea that tomorrow is kinder and prettier than today.
What about you? What are your favourite themes?