The Active English Discussion series is put out by Pearson Longman, authored by Andrew Finch. He's an expat living in Korea, and the books are definitely geared toward the Korean market. In fact, they wouldn't make a lot of sense to those outside.
I've been using levels 1 and 2 for some classes, middle school students and an advanced university conversation class. They have been amazing for both groups and would work for high schoolers as well.
While there are a couple duds among the 20 topics, the majority are engaging, interesting and relevant and get some good conversations going. The best thing about the series is that they are amazing for multi-level classes. The questions are open-ended enough so that everyone can give an answer according to their ability and feel confident in it. And the readings are short enough so that even the weakest students can get a basic grasp of it and not get lost in the details.
I've been using one chapter for a 50 minute class and this is definitely not enough time. I could easily do 2 hours with all the material.
The students like it. It gets them talking. It's easy to teach because there's lots of interesting, varied activities. That's all I really need for a conversation class!