I have Black Sea by Caroline Eden. It’s as much of a travelogue as a cookbook, so it does make for an entertaining read. You might guess that it doesn’t cover the entire Balkan region…just the parts around the Black Sea.
It’s certainly not grandmas secret, but everything I’ve made from there has at least been well received by Romanians. Then again, it’s as good of a starting point as an American BBQ cookbook if you read it with the understanding that similar ingredients might yield quite different results regionally.