Well, I have read FUTL, and as Spider Robinson says in the intro, it really is not a novel, per se, rather a series of lectures–social, sexual, political, and most of all, economics, economic, economics, connected by the thinnest of “Buck Rogers wakes up in a future land” plots.
I will give no spoilers because, really there are no spoilers, the above is pretty much it.
Probably the most interesting bit (and the most casual Heinlein fan probably coud have easily inferred this from his other writings), Heinlein had no problems with open marriages and nudity, and it is revealed that he and his second wife, Leslyn,* had such a marriage and were nudists.
No big deal nowadays, but they were married from 1932–1947, so they had to keep low-key, I would imagine.
Heinlein fans will love seeing the genesis of many later famous stories–rolling roads, Coventry, etc., but most others will certainly be able to see why the book was never published (apart from the “racy” content), and will realize that it is being published now pretty much solely because of who the author was and as a historical oddity.
And boy does everybody smoke like a chimney in 2086!
Sir Rhosis
*Yes, Leslyn McDonald was his second wife. Virginia “Ginny” Gerstenfeldt, who is often referred to as his second, was actually his third. Heinlein was married for about a year in the late 1920s.