The Diamond Cave Mystery

This book was published the year I was born. I recall reading it when I was a kid and being imressed by the mystery.
I wanted to see how it held up after all these years.
I think it's still a pretty interesting mystery and a fun adventure.
There are cultural issues (the only women in the story are mothers whose only job is to stop the fun).
As an adult, I appreciate the lecture the kids get about how important it is to not disrupt ancient sites,
If your kids read it, you might have to explain some stuff about telephones in here.