Good to have your company, SY. The Sony range is good, sound hardware. Its software, though leaves much to be desired.
I'd suggest the first thing you should do is to download the free and excellent Calibre Library software (which thousands of us here use). It's at
http://www.calibre-ebook.com. You can then download books (bought or free) from anywhere.
Calibre will automatically catalogue your library for you and even convert from one format to another if a book isn't padlocked by DRM. You then simply upload to your device in seconds via USB cable to your PC or laptop. You can delete books from your Sony reader any time, safe in the knowledge that the titles are still safely housed in your Calibre library for future reading.
Also at Calibre, there's a new 'Get Books' feature that lists publishers' titles and clearly shows which are DRM-free. Its 'Open Books' feature lists only publishers and titles that are ALL guaranteed to be free of DRM.
Sony and Calibre is a marriage made in heaven, SY. Good luck, happy e-reading and best wishes. Neil