To learn. Currently most of my non-fiction reading is in the area of natural science (I'll read any book for the layman written by a field biologist that comes into my hands) or memoirs about animals. I'll read a few books about contemporary politics and a sprinkling of other things that catch my fancy. But you can track the topics I've been interested in by looking at my bookcases: Old West history, Japan, herb gardening, etc.

Now, that's not to say that you can't learn from reading fiction. I've learned a lot about different eras by reading books either written in that era or about that era. My knowledge of 20th century Britain is shaped by Agatha Christie who (with one exception) set her books in the time they were written, so they show the change from WWI up to the late 60s/early 70s.

I read the Cadfael books and learned a lot about "The Anarchy" (which was a period I'd never even heard of) and life in a monastery. I finally understand the difference between monks and priests because I had thought that all monks were priests.

When Kerry Greenwood writes a Phryne Fisher book, she chooses some topic to study up on in order to include it in the book.

So even in my fiction reading, I prefer stories that I learn from.