Revolt in 2100 is another installment in Heinlein's Future History arc. Several major figures in that arc feature prominently here, and it takes place some time after the rise of the ayatollahs foretold in Stranger in a Strange Land. We get considerably more context for Scudder, and the origins of Libby in these three interconnected stories. This is about the height, and fall, of the united states theocracy (that in these times feels increasingly likely).
2100 is a bit of a melange...Heinlein's future history world and timeline building is at the forefront, but we get a taste of the military science fiction that Starship Troopers is known for and the social commentary and social engineering some of his later works like Stranger are known for.
As with some other early works, there is also more contradiction in his themes and social commentary than one might be used to with Heinlein. Its also easy to overlook if one approaches this expecting the typical themes that turn modern readers off Heinlein. Though religious dictators are presented in a (deserving) negative light and religion overall as hypocritical and unnecessary, several religious groups (notably the Mormons) are instrumental in overthrowing them and presented as quite reasonable folk. Similarly, the main organized resistance seems to all be part of an only loosely disguised version of the Freemason's, who are famously religious in origin and practices.
As usual, like Spinrad says, any Heinlein is good scifi and worth a read. However, I think for the modern critical reader there is a special wealth of things to contemplate is we can approach these early works with an open mind.