Mom sends young boy to buy cereal. Instead of the supermarket, he goes to run-down neighborhood store. The cereal is not good, but the back of the cereal box is part of a set that combines to build a model of a Victorian mansion. Boy returns to store to buy more of the cereal, builds mansion. Ghost of sad young woman appears. She was the daughter of the cereal manufacturer. The mansion had been torn down, the rest of the cereal boxes had been discarded, and this is the last model of the house existing. She had been in love, forbidden to marry, and died in grief. Meanwhile, the boy befriends a sad old man. Eventually, he realizes that the man and ghost had been in love, many years earlier. He races home to get the house, and finds that his mother has cleaned his room, and burned the house in the incinerator. Pre-1970s.
Stump the Bookseller
New format, same book stumper solving.
Not an exact match, but it could be ‘The Serial Garden’ by Joan Aiken. It’s in a book of the same name about the Armitage family, who frequently have amazing things happen. The cereal boxes form a garden. The girl gave a book containing the picture to her maid, to give to her lover; but the maid threw it away-so the cereal boxes were the last copy.
Sounds a lot like Joan Aiken’s story called “The Serial Garden”!
The cereal’s Brekkfast Brikks and the sad old man is the boy’s (Mark) music teacher (Mr Johansen). The sad young woman is a “German princess had been lost to him by an unfortunate bit of amateur magic.”