I am looking for a children’s mystery book about several siblings who are spending the summer in an old house and find several paintings hidden in the house by a deceased but famous painter. It seems as though their grandmother is with them and they spend time picking blueberries. I thought the name of the book was Blueberry Summer or The Blue Boy but these titles don’t match the book I remember. The book is about 50 -60 years old.
Mystery of the Auction Trunk?
https://www.goodreads.com/book/show/10190735-mystery-of-the-auction-trunk
Try “Mystery of the Auction Trunk,” 1956, by Elizabeth Honness. The children pick blueberries and they find paintings by a famous painter hidden in the house. The woman is not their grandmother but an elderly friend.
Possibly “The Mystery of the Auction Trunk” by Elizabeth Honness? Here’s the description from GoogleBooks:
“Nancy, Barby, and Doug Holland looked forward to summer in New Hampshire without realizing what exciting secrets came with their new home. The summer would hold more than swimming and horseback riding, blueberry pancakes and picnics at the lake, but they didn’t begin to guess how much more until Nancy bid for an old trunk at a country auction.
The Hollands were vacationing in an old house which had once belonged to a New Hampshire primitive artist whose paintings had lately become fashionable and valuable. A menacing art dealer, Mr. Cummings, was on the trail of yet undiscovered paintings and would stop at nothing to get hold of them. The children were afraid he might even get their marvelous house away from them.”