Heinlein's first published novel, published in 1947, was 'Rocket Ship Galileo'. It, like many of his earlier novels, is often put in the 'juvenile' section of the library. This is not really accurate; the book is far closer to 'Harry Potter' than 'Hardy Boys'.
The science involved is almost as laughable as the science in the Jules Verne story 'From the Earth to the Moon'. One professor and three teenagers throw together an atomic rocket on a shoestring budget, and it works perfectly, taking them all the way to the moon on the first attempt. In order to enjoy it, you must forget everything you know about modern science as it relates to space travel and nuclear reactors. But if you think of it as a fantasy book, you can have a lot of fun reading it.
Actually, Heinlein really did try to get the science right. There are several good passages about the scientific method and the philosophy of science and mathematics. He does make an attempt to show the radiation dangers of a nuclear reactor. The problem is that very few people really knew the proper science back then. At the time, no author really understood just how difficult and expensive it would be to escape the Earth's gravity well and make a working space suit.
As in many Heinlein books, there is a big plot twist. The plot twist is ridiculous, incredible, laughable, pure pulp sci-fi, and exactly what the story needed. It basically forces you to shut off your critical analysis of the book and just go along for the ride.
This book is definitely a product of its time, and it is not for everyone. Still, I can think of much worse things to hand to a teenager who is interested in science and fun stories.