I'm not really sure why this memoir was so controversial back in the day. I suppose that it was a shock to the general public in the 40s that royals are, in fact, humans with opinions, feelings and personal lives. Suprise!

The biggest take away is really how important Nannies, Nurses and Governesses are to the children born into families of the rich and famous. In this case, Marion Crawford was with the royal family for nearly seventeen years—from the princesses' childhood right up until their early twenties. 

This memoir goes into detail on a range of topics including Elizabeth and Margaret's schooldays, their close relationship with each other, the shift in dynamic between them and their parents after the coronation of George VI, the abdication crisis, the war years, the blitz, Elizabeth's involvement with the auxiliary territorial service, Elizabeth and Philip's courtship and the years immediately post-WWII including the royal wedding and the birth of Charles.  The influence of Queen Mary also comes up quite a lot, including her mentorship of Elizabeth and her insistence on both girls getting a more rounded education. 

Overall, it was an interesting read. A bit saccharine at points but decently written. If you're looking for something scandalous/gossipy though, I would look elsewhere.