Was it an Enid Blyton story about a man who didn't have any common sense? I remember a short story about a man who did al kinds of silly things and one time he bought a block of ice cream for his wife on a hot day and put it under his cap to protect it from the sun. It melted and dripped down his face!
Another time he needed to make a journey on a train but sitting with his back to the direction of travel made him feel poorly. His wife told him that he should ask the person opposite to swop seats with him. When he arrived home he felt poorly and told his wife he couldn't ask the person opposite to swop because no one was sitting there!
As a child, I read a briiliant book about two children trying to solve a mystery. It involved a precious pendant, a wizard, a cave and several other things but I can't remember the book title at all. I am sure it was a well-known book at the time and I wish I could find it again.