Most of the historic record of the GDR has been set by FRG historians running victory laps and is based on anecdotal evidence at best, mythology at worst. A lot of people also attempt to equate the GDR with the third Reich (which is insane to begin with, but that's what people are taught here).
Preferred languages would be German and English. I could make Russian work, but not very well.
Edit: I know about John Green.
Idk how scientific it is, but "Stasi State or Socialist Paradise" gets right down to brass tacks and says that while most western propaganda relentlessly focuses on the problems and real or imagined failures of the GDR they're going to lay out the things the GDR did right, the problems they solved, the way the people of the GDR busted ass to build a better society. It's a very compelling book that upended my view of the GDR, but it does need to be understood as a work of polemic. (Polemic is good and I endorse it).
Yeah, forgot to mention that I'm familiar with that one, although I only read excerpts.