Thank you for your help. I got it to work with the url "book.me". However, I edited the instructions in steps 1, 2, & 3 as seen below and it seems to be working fine. Replacing what's in bold with what's in parenthesis.
If you can see that this would be a problem, please let me know.
Thank you again.
Step 1: Change the host name (hostname)
In the last line of the /etc/hosts file, replace moodlebox with learn.example.com.(book)
In the /etc/hostname file, replace moodlebox with learn.example.com (book) (this modification is not necessary, but highly recommended).
Step 2: Adapt the configuration of the nginx web server
Change the file /etc/nginx/sites-available/default, replacing moodlebox with the full domain name (FQDN) learn.example.com (book) in the server_name directive.
Step 3: Adapt the DNS server masquerading configuration
Change the file /etc/dnsmasq.conf, replacing home by learn.example.com (me) in the two lines that start with domain and local. Comment out or delete completely the line starting with address.
Step 4: Adapt the Moodle configuration (Moodle URL)
In the file /var/www/moodle/config.php, on the line beginning with $CFG->wwwroot, replace the URL http://moodlebox.home by http://learn.example.com. Do not add a slash at the end of the URL.
Step 5: Restart the MoodleBox
In order to apply these changes, restart your MoodleBox.
Step 6: Replace Moodle URLs
Access your MoodleBox through your browser using the new address http://learn.example.com/ and use the URL replacement tool at http://learn.example.com/admin/tool/replace/index.php to replace URLs in the Moodle database.