AZ Jane, not sure if you already know this (and I apologize if you do), but turning off the Wi-Fi on your Kindle Fire will conserve the battery. When I'm just using mine to read (after the book/magazine/whatever is already downloaded), I simply turn off the Wi-Fi until I'm ready to download again. Just think about it this way - when the Wi-Fi is on, it's always "pinging" back to the internet to see if something is ready to download, which uses battery life.
As to your original question, as others have said, the special offers don't bother you while reading. I've actually bought several things because of the special offers!