Great question! I generally manage about 200 pages an hour, depending on the book (light reading, or non-fiction; I prefer the latter). I read English much faster than German. I'm through an "average" English book of 400 to 500 pages in about two to two and a half hours, whereas it sometimes takes me almost an hour longer to get through a German book of the same length.
My high school had speed reading courses, and I was exempt after the first lesson (reading and comprehension test), because I read faster than the teacher.
My siblings were also "excused". I'm from a family of bookworms, and we were only allowed half an hour of television a day as children, and an hour as teenagers. We read.
I should mention that I majored in German and minored in Spanish/Latin American Lit., and became quite accustomed to having to read three or four foreign-language novels a week just to keep up with my classes. That was habit-forming.
I love marathon reading sessions! Since the new Harry Potter book is coming out next month, I decided to reread the last four books this past weekend, and actually managed it (yes, I did cook, clean, do laundry, and visit TCS), but rereading a book is much faster than reading it for the first time. If I'm on vacation, I average about seven to ten books a week.