This novel was awarded the retro Hugo for best novel of 1951, awarded in 2001.
This is considered one of Heinlein's juveniles, meaning it was felt suitable for teens and young adults (and adults), at least in 1950.
Many of Heinlein's novels fit this category and most of them, like this one, are extremely good stories for adolescents and adults alike. He never talks down to the reader, but unlike some of his adult novels, they tend to avoid overt preaching of his personal beliefs about government, military, and economics.
To avoid any spoilers, I'll just say that this, like many of his juveniles, could be called a coming of age story, and I thoroughly enjoyed it.