I often have trouble focusing when I'm reading, and end up drifting into my own thoughts or reading the same sentence over and over. So that makes me a slower reader. When reading non-fiction or less descriptive books I kind of skim and read pretty quickly. When I read really descriptive books, though, I stop to take in and visualize every word, so that slows me down.
Oh and congratulations on your first posts, quietkidprofile 