As far as content, there are other places besides Sony Connect to find modern scifi e-books that can be used on the Reader, like
www.baen.com,
www.stevejordanbooks.com and others.
If you "must" have everything electronic, you probably have to stay with paper, or get a book scanner to scan paper books you want to read. But while Sony is aggressively trying to add content, there isn't any online e-book seller that can match the coverage of titles at BarnesAndNoble or Amazon.
The other thing to keep in mind is that if you are buying all your books at Sony Connect, they are for the Sony Reader only. You won't be able to read them on other platforms because of DRM. It's not special to Sony, but is widespread across the e-book industry. And while it's "bearable" for most people, it is something to keep in mind if you were planning to build a long term scifi library.
Thanks for the $25 off tip. Anyone have the link and details?