Permit, allow, hide, control: that's it!

Easy to install; allows to overwrite the native WP roles in a flexibel way. You grant capabilities to a “group”, and add each WP user to one of your groups. Then you work on your pages and set up required capabilities for some pages – and only logged-in users, which belong to a group with those capabilities, can see the pages. Exactly what you need for a “Members only” space. And it fits to my WP version 4.2.2. Excellent!