I like to recommend Methuselah’s Children because it’s where we meet Lazarus Long. The beginning of the Future History, although Lazarus did meet Pinero.
What do you recommend and why?
In my opinion, his earlier stories were alot easier to read. To this day I still recommend Starship Troopers and Citizen of the Galaxy, not just to anyone new to Heinlein, but anyone looking for a good story to read.
Depends entirely on their age and tastes. But if I know nothing of them, Double Star. It’s quality without being too pushed in any particular direction.
I like his early 50s-60s work (some were written for youth):
The Star Beast
Tunnel in the Sky
Starship Troopers
The Moon Is a Harsh Mistress
And then there is the whole Lazarus Long saga, which contains some controversial sexual ideas (incest/pedo). IMO the first books in the saga are better.
