I was deferring to the other two, as I have basically no book knowledge and have just been reading all their crazy comments :D

I do have some links here but many of the links are video (which I haven't yet watched) or not in English (though for small things google translate can be used). I have read Volume 1 of Wilhelmine's memoirs in English translation (linked from that page), which definitely does make it pretty clear what an absolutely crazy family Frederick the Great was from, although depends on your tolerance for abuse (his father being quite abusive both physically and emotionally, and their mother being emotionally abusive to Wilhelmine). Volume 2 is less relevant to this discussion and I foundered in the middle of it.

If you're interested in Maria Theresia, there is apparently a good biography of her by Barbara Stollberg-Rilinger coming out sometime soon in English translation; I'm definitely going to get it when it comes out and will post about it. selenak has read it in German and has good things to say about it.

Also, that is two more things than I knew before all of this started! (Although selenak told me (2) last year.)