The Grumpy Celt said:
Why not?
If you had to recommend a single, adult Heinlein book, what would it be?
Because it, like
Starship Troopers seem to have a tendancy to cause people who read one of those works to regard Heinlein as a one-dimensional writer. Those who read
Starship Troopers first seem to view him as a hyper-militaristic cowboy. Those who read
Starnger in a Strange Land first seem to view him as a dirty old man obsessed with sex. Neither is very accurate.
For an adult novel to read first, I would generally recommend
The Moon Is a Harsh Mistress or
Double Star. Alternatively, I might suggest one of the collections of his shorter works, like
The Past through Tomorrow or
The Green Hills of Earth (any compilation that has
The Must Roll,
The Man Who Sold the Moon,
Coventry,
Logic of Empire, and/or
If This Goes On. . . is worth reading).
I would definitely
not recommend reading
Sixth Column (also published as
The Day After Tomorrow) or
Farnham's Freehold unless you can put his writing into the social context in which he was writing, because if you don't get the social context in which he was writing, one could come away with the opinion that there are some rather unenlightened elements to those books.
I would also suggest avoiding his later works at first (
I Will Fear No Evil,
To Sail Beyond the Sunset,
The Cat Who Walks Through Walls, and
Time Enough For Love), because Heinlein wrote about some rather experimental sexual arrangements in those books. If the reader is religious and easily offended, I also wouldn't recommend
Job: a Comedy of Justice (God is portrayed rather badly in the book).
Despite what has been said here denigrating his YA fiction, most current science fiction authors will usually say that the books that inspired them to get into science fiction were his books -
Red Planet,
Rocket Ship Galileo,
Orphans of the Sky and
Have Spacesuit - Will Travel are often cited. Not a YA book, but a lot of authors cite
Beyond This Horizon as an seminal inspiration as well.