apt-listchanges is a small tool which shows changelog entries for Debian packages. You can install it from the repositories:

aptitude install apt-listchanges

In case you ever want to make changes to its configuration:

dpkg-reconfigure apt-listchanges

If configured correctly every aptitude upgrade will now show the corresponding changelogs for each package with the option to abort install. It’s even possible to mail the changelogs to a provided email address.