Frank and Joe Hardy, teenage sons of a famous detective, find a mystery to solve on their own when the Tower Mansion is robbed of a fortune in jewels and bonds. The caretaker is arrested, but the boys don't believe he's guilty.
I read the original 1927 edition and it is quite a trip back in time. By today's standards, the language is antiseptic and bland ("No slang please, not in Tower Mansion!"), but it's perfect for boys aged 8-10 who are just beginning to read chapter books. There's no danger, violence, or even much action to speak of; the emphasis is on the boys' resourcefulness and determination. Joe and Frank Hardy are relentlessly optimistic and straight-arrow good guys; in fact everyone in the story is wholesome and uncomplicated. Although the Hardys clearly obstruct justice by hiding clues from the police (who are portrayed as village idiots), they emerge as real teen heroes.
The story was serialized (and made more exciting) on TV in the fifties in
The Hardy Boys. The book's straightforward simplicity is reminiscent of "The Boxcar Children," another kids-know-best children's novel.