You could put your text in a part of your directory structure not available via HTTP request.

In other words, if my webpages are in ~/public_html, and my CGI scripts are in ~/public_html/cgi-bin, I could put my content files that I want to "hide" into ~/content (ie, not within the area that is within the document path available to the HTTP server).

Then you would write a small set of CGI scripts that simply do the work of authenticating individuals and grabbing data from the files in ~/content.

Your server should be configured such that ~/content isn't available by direct HTTP request, but from within your scripts, it may be made available; the scripts may get at your content path.

Update: Another idea would be to put your content into a database that itself requires password access. The scripts would have access, but outsiders would have no way of directly getting at the DB's contents.

...just a thought.