Private WP will make sure people can only read your blog after they log in. Already logged in users will see no difference. 
Users who are logged out will get the login page, and only that.
Use this for private “intranet style” blogs, or closed community sites.
Note that the plugin offers no options. Activate it to turn it on, deactivate it to turn it off!
If you also use Windows Live Writer, be sure to check out <a href="https://wordpress.org/extend/plugins/wlw-login/" rel="ugc">WLW Login</a>.

Private WP

This plugin is simple and robust (it works even it hasn't been updated for 2 years) ... yet it does exactly what it should do: lock the whole site with the login site.
For most of our beta sites this is exactly what we need while the clients editing the site until it is ready for golive. No unnecessary additional features that need your focus ... just active it and its runs.



Does what it should do

Makes your blog accessible only to logged in users.

Private WP 2 will make sure people can only read your blog and rss feeds after they log in. Already logged in users will see no difference.

Private WP 2

Makes your blog (including RSS feeds) accessible only to logged in users.

Private WP vs Private WP 2