I'm almost always reading at least one of both, but usually two nonfiction and one fiction. Basically: have two topics for learning to avoid monotony; and have a fiction around for pure diversion.
Currently I'm working on:
Fiction:
- House of Leaves by Mark Z. Danielewski (rereading)
Nonfiction:
- Solidarity Economics: Why Mutuality and Movements Matter by Chris Brenner and Manuel Pastor
- Democracy and Economic Planning by Pat Devine
EDIT: Oh yeah, I'm also listening to Wool by Hugh Howey (first book in the series the show Silo is based on)