I don’t recommend this book for an intro to RAH, because about halfway through stuff starts happening that makes no sense without reading some other books first. Methuselah’s Children and Time Enough For Love, at least. The first is a great intro to RAH, the second is a bit heavy but can be done— as one of his later books it gets into some controversial ideas he liked to write about.

To see what you’re getting into, https://en.wikipedia.org/wiki/Future_History_(Heinlein) and https://www.heinleinsociety.org/faq-frequently-asked-questions-about-robert-a-heinlein-his-works/#Does-the-Future-History-and-the-World-as-Myth-relate-together

Feel free to ask over in https://lemmy.world/c/the_heinlein_society if you like any more info!