Reading speed

You know, I thought I was a reasonably fast reader until today. Now, as far as I can tell, it took me longer to read the OotP than almost anyone else. It took me a whole 10 and a half hours. cliosfolly seems to have finished in 5 hours, innostrantsa in 6.5, and aliciam made it through in an astonishing 3 hours.

How do any of you get anything out of a book at that speed?