I found the issue. This Cisco Press document is incorrect in its example. In the example they show "logging trap informational". In fact it appears that "logging trap debug" is required.
Enabling Syslog: Example
The following example shows enabling NAT entries into syslog.
Router(config)# logging on
Router(config)# logging 1.1.1.1
Router(config)# logging trap informational
Router(Config)# ip nat log translations syslog