It's actually three more excluding R;N. They are Zetsuen no Tempest, K, and Shin Sekai Yori. Psycho Pass is another one though the mystery becomes transparent by episode 7. I also recommend Hyouka if you haven't seen it already. While the premise is a bit plain, the show I think inspired a lot of these mystery themed series we are seeing this season.
Caught up to episode 7. This is a seriously good show when I take all 7 episodes in context. The gradual build up to a very interesting mystery that is adding to the suspense is very effective at building up my anticipation to what's to come next. In episode 6, when Yashio was going to take the stairs to the basement, I'm practically yelling.... don't go down, don't go down. This has become my most anticipated show, right behind Zetsuen no Tempest. I'm also a fan of characters like Yashio (in daily life too) who is non-intrusive, laid-back, and knows to assert himself without subverting anyone.
There has been a severe drought of mystery anime (supernatural doesn't count) that has lasted years and now suddenly, we have at least 4 new series that has good to very-good stories emerged into this new season. It's a delight to be a mystery-fan this season that's for sure.