History

Stasi State or Socialist Paradise is the book I've read on it. It focuses mostly on the good aspects (and especially makes very good comparisons to other countries at the time) but also mentions and to some extent contextualized the bad aspects too. I think it would probably be a good starting point despite being more editorialized than a strict history book, and it has citations for further reading.

Side note: I read that book just before visiting Berlin, and of course I had to visit the DDR Museum there. It was a real shock seeing the propaganda there after reading the book. It almost felt like satire of anti-DDR propaganda. At one point the museum mentioned that people in the East had more sex on average than people in the West, and the museum tried to explain it as "there wasn't much else to do in the DDR." That and the fact that people repaired things ("a DIYers heaven") were the only good things the museum had to say about the country. They even said that its revolutionary child care systems were just communist indoctrination, and had nothing to say about women's rights or anything like that.