Oh, I've read it and it's on my bookshelf. Just something like 3 or 4 decades ago :-) It was never actually a particularly favorite Heinlein for me though so I haven't re-read in a very long time if ever.
Hey same here, and Heinlein was my favorite author for a very long time. That particular book just never really did it for me.
Stranger in a Stranger Land was probably more of particular time and place that a lot of Heinlein's works. Although it came out at in 1961--mostly predating the counterculture era in the US, its mainstream cross-over appeal was definitely tied in with the Summer of Love etc. later in the decade.
1968 would indeed be about the right time period as "I grok Spock" bumper stickers appeared around then too.
Grok is not simply understanding or knowing a thing, it’s knowing that thing so well and all the things related to that thing, and understanding all of your feelings associated with that thing, that it becomes a part of you. At least, that was my interpretation of it.
Heinlein’s explanation and exposition is more detailed in the actual book. If you have not read it, highly recommended.