Stranger is one of the few Heinlein books I've not re-read. (I've re-read
Friday, but it's not a favorite.) I suppose I should re-read
Stranger at some point, just to see if I get more out of it on a second read. I liked the premise well enough, but didn't engage with any of the characters.
I've often thought
Podkayne was probably set in the same universe as
Red Planet, and possibly also
The Rolling Stones, though perhaps not, as the flat cats would surely have been in more evidence in
Red Planet, and would have distracted from the character of Willis.
Sometimes it's a bit hard to tell, though, as Heinlein would re-use some ideas, but shift others for the needs of the story.
Stones would appear to be set in the same universe as
The Moon is a Harsh Mistress, however.
Hm. Maybe I'll re-read some Heinlein tonight.
Thief of Time isn't really grabbing me yet.