All the Secret Seven books have a similar style, so if you like one you should like all. They are like the Five Fibd-Outers, only written for younger children, so the plots are simpler. But the idea is the same, a group of children who investigate mysteries in their own home town. Instead of Fatty as the leader, the Secret Seven has Peter.

In this one, the Secret Seven's usual meeting place is being repaired, so they have to find a new place. They find a small cave, but their things start disappearing from inside, which is the start of the new adventure. There's also more rivalry with Susie. ( )

The adventure-mystery plot is just realistic enough that a young reader might imagine experiencing such things himself, but meaningful characterization is sorely lacking. ( )