You could also try Sony Reader. That is designed to go with Sony eReader devices but is a free download that can work standalone, and can read Adobe DRM books.
I don't like it very much, but you may happen to prefer it to ADE.
http://www.sony.co.uk/support/en/topics/reader-for-pc
You might also try the older ADE. That gives a better reading experience to my mind than the new one, as well as having many fewer bugs.
There are lots of bugs in ADE2.0. Try replacing ADE2.0 with the older but more reliable v1.7.2.
(You can have them both installed at once if you like.)
Version 1.7.2, it is a little difficult to find, available on Adobe site for Windows and for Mac.
http://helpx.adobe.com/digital-editions/kb/cant-install-digital-editio ns.html
The forum software is sometimes corrupting the link above. There shouldn't be a blank in 'editio ns.html'. The following redirects to the same page: http://tinyurl.com/diged172
For non-DRM books, try Calibre. http://calibre-ebook.com/
