The Diary of a Young Girl by Anne Frank

The parents keep an adult book (a book about women) to themselves. We are never given the title, only told that Peter snatched it and caused an uproar.

Last week there was a brief interruption in our monotonous routine. This was provided by Peter -- and a book about women. I should explain that Margot and Peter are allowed to read nearly all the books Mr. Kleiman lends us. But the adults preferred to keep this special book to themselves. This immediately piqued Peter's curiosity. What forbidden fruit did it contain? He snuck off with it when his mother was downstairs talking, and took himself and his booty to the loft. For two days all was well. Mrs. van Daan knew what he was up to, but kept mum until Mr. van Daan found out about it. He threw a fit, took the book away and assumed that would be the end of the business. However, he'd neglected to take his son's curiosity into account. Peter, not in the least fazed by his father's swift action, began thinking up ways to read the rest of this vastly interesting book.