I never read ‘The Moon is a Harsh Mistress.’ As a youngster I read Heinlein’s ‘Starship Troopers’ and loved it from the very beginning, though it slowed down after the first few chapters. I tried to read some other Heinlein, and he could have some fascinating plot ideas, but too many of them seemed to eventually just devolve into sex orgies between the characters and I lost interest in Heinlein books after seeing this in more than one of his works.
You must have read mostly his very late stuff. Little of his early to mid career work went there - on the other hand, the ‘orgy’ books seem to have been prescient about how society is going anyway.
You should probably go give The Moon Is A Harsh Mistress a try. It’s available in eBook format cheaply from the usual sources. The math and physics in the book are dead on - and if you weren’t alarmed about the US’ retreat from space and current cession of the moon to the Chinese, you will be afterwards. Heinlein spent the rest of his life after the Apollo program ended up going nowhere desperately trying to get the US Government to realize what they’d done. Thanks to Democrats like Senator Proxmire, most of the government still doesn’t know or care.
The Moon is a Harsh Mistress is my favorite book from Heinlein for just an enjoyable scifi read.