I read all kinds of books and magazines. I have a tendency to focus on a writer or a theme and then read my fill. For example, I picked up a memoir by Jen Lancaster, Pretty in Plaid, and it was hilarious, so I read all she had published. I watched Young Victoria and next thing I knew I was reading books about Queen Victoria and British history (let's just say the movie took great liberties with history to craft a love story). Right now, I am focused on SK and have checked out the Essential Stephen King by S. Spignesi. I also have the Girl with the Dragon Tattoo on my reading list. And then there's religion...but I won't start with that here. LOVE getting lost in the encyclopedia and dictionaries and Wikipedia.
For me it's history (mostly European and ancient) and books on physics (particle, theoretical, quantum), astronomy, and the occult/folklore. I also read true crime, sport biographies (typically those of football (soccer) managers), linguistic/language theory and books on writing. Including but not limited to On Writing (though it's the best by some considerable way).
Oh, and I'm trying to learn/improve/perfect my skills in French, German, Russian, Polish, Estonian, Spanish, Italian, Danish and Swedish. It gives me something to do when not writing that doesn't seem to affect or use the bits of my brain that I used while writing, so I can get back to the mss after a break of 10-30 minutes and still feel refreshed.