Reading is highly subjective. Most books will tell you to read the topic sentence and skim the rest. I personally think that is a$$ backwards. But for others it works. For me, I need the details to help me understand the whole of the passage.
Princeton Review says that you should spend the majority of your time on the questions, since you don't get points for reading. To me, that's once again a$$ backwards thinking. If you spend the proper amount of time reading and fully understanding the passage, you'll be amazed at how quickly you can get through the questions rather than sifting through the passage for answers.
So again, it's subjective whether you should speed read, but there's nothing wrong with reading slowly and absorbing everything.