Please suspend you disbelief when you read the plot description; you would have hard time keeping a straight face. Three teen boys love to build rockets and hope to win their school science prize with a successful model. One day a university professor offers them to help build a real spaceship in exchange for taking them to the Moon on the said ship. Do you think any normal teen of early fifties would refuse the offer, or consider refusing it even for a second?
If you think this all sounds too far-fetched, imagine yourself in your early teens. I did and I realized that my parents would not be able to pry me off this book with a crowbar at that age. I also felt nostalgic for times when teens could be teens and among other things make things go boom without a police squad coming at them in full force as terrorist suspects. Kids were not as sheltered as today and still somehow managed to survive to adulthood. It is also interesting to note that there was a lot of attention given to three teens' scientific achievements, but their sport wins were not mentioned at all: science education mattered in fifties more. Now get off my lawn!!!
This is the first published novel of the classic of science fiction and it shows. For the risk of alienating a lot of people I will say that juvenile fiction is where Heinlein really shines. My opinion still stands after reading this book. If you want to criticize it please keep in mind that is was written not only before the first space flight, but also before the humanity took a look at the Dark Side of the Moon (I do not refer to the excellent album by Pink Floyd here). It also contains some fun scientific facts related to space flight that became such common knowledge today that we actually forgot them again.
As I already mentioned my teen self would love the first two thirds of the book. The last past became ridiculous even for intended audience. Thus I was about to give this book solid 4 stars but the last third is a big letdown worth 2 stars only. This gives 3 stars on average and I will leave it as it is: quite a fun read with some laughably bad parts.