Well, this is hard! I checked what else our buddy Horowski has to offer. Seems he has a new book coming out in November which could be just the ticket, as it's about the families Richelieu, Bentinck and Liechtenstein between the 17th and the 19th century. But it's months till November, and the only other book that's available sounds way more academic and more like it's his published dissertation. It's also hideously expensive (69 Euros!).

Now, there are Sophie of Hannover's Memoirs in German, which have the advantage of being a) short, b) not hideously expensive (ca. 15 Euros on Kindle), and c) this includes the introduction essay for the new translation and the footnotes. I found them very entertaining, informative (with the caveat that they end shortly after Sophie's turned 50, so don't expect anything about the Hohenzollern in them) and often witty, see my write-up. But there are also a lot of people mentioned you might not know yet (though there are footnotes telling you who they are). Btw, there's an English translation out there as well, I think, at least there's one at the Stabi, which I'm not interested in since I have the German translation at home.

(ETA: another advantage of the Sophie memoirs in German is that the translation is recent - the Memoirs were written in French, after all - , which means you don't have to put up with Baroque German. Which you would have in any edition of Liselotte's letters which isn't a translation into English, so I can't rec it to you./ETA.)b

If you want to branch out and try fiction after all, I could also reccommend the book which I've gifted to cahn in English, Christine Brückner's "Ungehaltene Reden ungehaltener Frauen". This has the advantage that the fictional speeches by various real and fictional ladies are all short texts (and the book itself is also a slim volume), and every text stands on its own. I don't love all speeches to the same degree, but several of them I do, and there is much wit there as well as emotion.