I’ve had this hanging around for ages, and eventually read it last week – it is very short, only 112 pages in my Penguin edition, and the original was only 93. Rasselas, as the title declares, is a prince of Abyssinia, who lives in a happy valley of the kingdom where he and his friends and family are preserved from all disturbing outside influences. With his friend, Imlac, his sister Nekayah, and her companion Pekuah, they tunnel out of the happy valley in search of adventure and take up residence in Cairo. They meet a deranged astronomer, and get him back in touch with reality; they get their adventure when Pekuah is kidnapped by Arabs; but she is rescued without too much drama. At the end of the book, they conclude that their dreams are unattainable and resolve to go back home.
I was interested that the action is exclusively set in Africa. There is mention of Europeans being in Cairo, and this making it a cosmopolitan city, but I don’t think we meet any of them. I was also interested that the astronomer character, whose delusion is that he is in sole control of the planets and the weather, is aware of the moons of Jupiter. We are clearly meant to read the African characters as disaffected young English men and women, and that is how they are portrayed (with a touch of Orientalism) in the illustrated editions on-line; I don’t think Johnson is really trying to say anything about Africa (though he had translated Jerónimo Lobo’s book about Abyssinia twenty-five years earlier).
It’s striking that this was written 250 years ago this month, the same year (1759) as Candide, which has a similar basic concept, but the timings I think are such that neither Johnson nor Voltaire can have much influenced the other. It seems to have been the last fiction (indeed, the only prose fiction) that Johnson published. It is somewhat pessimistic but very engaging.