Reading "Structure and Interpretation of Computer Programs"

I am reading Structure and Interpretation of Computer Programs. I can't believe that they use this as a textbook for an introductory course at some schools. It's really a pretty hard book. I think I am going to have to skip a lot of the exercises and material if I want to finish the book in a sort of timely manner. A free online copy of the book is available. I'm reading that version right now, but I think I will buy it eventually. (If you look at the Amazon comments you will see that Peter Norvig and Paul Graham highly recommend this book.)