How to measure engagement in uncommunicative class
One thing that I've heard suggested is a "one-minute assignment": at the end of each lecture, ask students to write down two things and turn it in: 


A one-sentence description of what they thought was the most important point of the lecture, and
A one-sentence description of what was most unclear to them during the lecture.


These questions give you a sense of what the students thought of the lecture, and what didn't work.