Welcome to MobileRead, CarolC!
We have books here that you can download for your 600 in either the lrf or epub format. I prefer the lrf because it is fully justified but it is certainly a personal preference. Just click on [Ebooks] in the blue strip at the top of the page and select the format you like. Look through all the available books and then download it to a directory of your choice on your computer. You can then Import that file into your Sony Ebook Library software or use
Calibre, a much better library software that is available here at MR. Good luck.
Happy Reading.