I usually only read non-fiction books which I had purchased in MS Reader format.
However, I looked at Sony eBook Library and picked 7 books I'd like to read for the rest of the year. All were published from 1997 to 2007. Prices for most were reduced to $ 8.96. A few were priced up to $ 11.20.
Most were not available in MS Reader format. One which was available in that format was cheaper by $ 1.00 in the eBook Library.
It appears Sony is now competing agressively with Amazon Kindle in books available and in price.
I usually read two books at one time - one in eBook Library and the other in MS Reader format. I've decided both of my two selections will now be in eBook Library format.
I do most of my reading on my 24" HD Monitor on my PC and only SUPPLEMENT it with occasional reading on my Sony PRS 505 Reader.
Amazon does not allow their books to be read on a PC. That is a significant flaw for someone with my reading habits.