It's working for me. Sorry for some basic suggestions, but can't think of anything else.
Are you sure you haven't got a control key (such as ctrl/shift or alt) stuck down?
Are you sure you have got focus on the reading page? (click on it with the mouse).
ADE2.0 is full of bugs, but I can't quite think where this one might come from.
Apparently this bug still has not been fixed. I bought a Win8 computer 09/09 and just downloaded ADE, checked out one of the free books FROM ADOBE SITE and the bloody thing will not allow me to get off the cover page. Scroll wheel, Page Up/Down, even clicking the forward/back arrows... NOTHING WORKS!
Bloody brilliant technical support Adobe!
I don't see this bug on Windows 8, but several people do seem to have it.
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.
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