I've posted this elsewhere, but maybe this needs to be in a FAQ?
When I was having problems with eBook Library, this is the procedure Sony gave me to completely scrub the software from your machine:
Delete /Users/(yourname)/Library/Preferences/Sony Corporation
If you're not used to reading *nix style file names - /Library is in your "Macintosh HD". Stuff that begins "/Users/(yourname)" is stuff that's in your home directory.