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?
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.
One of his short stories from '41 “By his bootstraps” is a great time travel paradox.
And The moon is a Harsh Mistress solid story and a great into to orbital mechanics…
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.
The very first Heinlein book I read was The Cat Who Walks Through Walls. It featured Lazarus Long, and I went on to read many of his books.
Starship Troopers is a quick read, well worth it.
Stranger in a Strange Land is an all time classic novel, a MUST read.
Time Enough for Love
Have Spacesuit will Travel
Anything really.