Should be dpkg --status, not --show (page 149)
More...Reported on: 2005-12-03
In chapter 5. The Debian package management system on page 149:
The paragraph after the first code snippet on page 149 in section 5.3.4 states that dpkg --show is more or less the same as dpkg --info. Instead of the --show, this should read --status, as in the code snippet.