Making posts private to varying degrees, depending on user level

Hi, I hope someone can help point me in the right direction, to a plugin, or a codex page (the ones I’ve found on roles and user levels are outdated and/or incomplete) or even some guidance to my specific situation.

Essentially, I need 3 levels of users, all of them only readers and commenters, (so, no writing posts or anything like that).

I need a some posts viewable by anyone who stumbles across my site, some posts viewable only by registered members, and some posts viewable by people who are registered AND given “special permission” to view my really opinionated posts.

I can’t just use the password protect for that because I don’t want the people in the other levels to even know about the private posts, and if they are password protected, they will still see the titles.

I am thinking I would have 3 categories and somehow assign which users can view which categories?

Is there already a way to do this? I really appreciate any wisdom you can share!