ahh.. a common deception, but intelligence and IQ level does not affect how fast you read. How fast you read is how much you really want to absorb the information. Some texts can simply be quickly skimmed and key points taken. Some texts, however, require in-depth perception of the words where every important detail is critical. Also when people read for pleasure, they most of the time read at a pace where the events in the book can play along like a movie in their minds eye, an impossible feat if you read too fast. When you get done with a book, and take a huge test on it, and get 60's, 70's and low 80's then you need to ask, was it worth reading the book fast to brag about it too your friends?
My average is a 95 in school, and I read extremely slow. It takes me a week to read a 400-600 page 10 size font piece of literature when im reading for pleasure. However when I am skimming text books for information, a chapter takes me less than 5 minutes. When im reading textbooks that require thinking and notes and thoughts, it takes me quite some time because I place notes and reminders, as well as thoughts and ideas in the margins of the book.