What I discovered is not just that "Although 'tell-all' books regarding celebrities are somewhat commonplace now, Mommie Dearest was the first book of its kind" but that the term "tell-all" originated when the book was published.
I read the transcript of a Larry King interview with Christina Crawford, the author of the book and other books about abuse, and saw this:
KING: Did you ever feel there is a part of me here that is doing the tell-all?
C. CRAWFORD: That -- that phrase was coined after the book, so that was never my intention. The one thing that surprised me...
KING: You mean, tell-all resulted from your book.
C. CRAWFORD: Yes.
KING: The term "tell-all?"
C. CRAWFORD: Yes, yes. The one thing that surprised me was that so many people who knew did not understand that I was speaking as the victim and the survivor.
The King interview is really good--I recommend reading it if you want some more info about her and her upbringing. I'm tempted to read the revised edition of the book (with 100 extra pages), which was published on the 20th anniversary of the original release.