Thanks for this info about the computer-Kindle reader.
If you happen to have a Droid device (cell phone, tablet, etc) you can also install the free Kindle app for that and download books to it. I have a Nook Color to which I added a Droid SD card in the SD slot. It now works like a Droid tablet. I can read both Kindle and Nook books on it. But I mostly read on my Kindle 3rd gen because the battery lasts so much longer.