It's like some kind of fiction equivalent of a car crash, or possibly drugs. You know it's bad, but you can't stop yourself from reading it anyway.
Today I went to the library and got books 4&5 out to see if they're as bad as I remember them being. (I don't own them. And since I have to ration myself on book-buying, I refuse to shell out for them.)
I do own the first 3. Let's see--originally got Dune (the first one) from the library, bought a copy sometime later. The 2nd I bought used for about $1. The third I also originally got from the library (I was a library junkie). I bought it last week because I felt like re-reading it and Borders was having a "buy 2, get the 3rd for 50% off" sale.
The others I also got from the library, and never bought.
I really must do a 2nd-hand book browse when I go back to Huntington next week. There are 2 good used book stores in town. We don't have any by me. :-(