Read aloud to my kids and was enjoyed by all. The main characters (3 children of 12ish years old) were very proactive, industrious, capable, and in the end made sweet friendships with the older tenants of the apartment building. A silly mystery to keep the kids busy. Swimming at the beach every afternoon. A satisfying, tidy happy ending. Not fantastic literature, but a great summer read.
One thing to consider: at one point the little sister (3 years old) goes to visit one of the older ladies inside her apartment, without her families knowledge, and is told to keep it a secret. HUGE no-no in the modern world. This is a problem I often come across with older books, but of course we can just talk about it after reading. Turns out that the older lady has a pet monkey and is afraid of getting kicked out, since pets are against the rules.
Other fun talking points are Florida, hibiscus plants, coconut trees, seashells, and hurricanes. My kids enjoyed looking these up as they were mentioned in the book.