It's probably considered either utopian or dystopian science fiction, but it differs from the general sort of either. Published in 1923, it purports to be the memoirs of Lady Porstock, written in 1988, in which she reflects back on the times from 1915- 1972. Knox was extraordinarily literate, and had an unusually active mind, so even if you knew nothing of events in Britain during the time Knox is writing, since he can rely on history he has lived through for the first ten years or so of her reminiscences, and even if you did not follow the projection of some then current ideas into the future, you would still come upon lively bits of wordplay, jokes, social interaction, and witty social commentary not germane in any way to the plot.
And plot is the wrong word. This is a leisurely sort of stroll down memory lane, but for us, into the future, in the manner of watching old science fiction movies. Since Lady Porstock is the author, she pens the "Author's Preface". But there is an "Editor's Preface" before that, ostensibly written in 1988, the date her memoirs are released. Now it gets confusing, "Do not despise the past," she advises the prospective reader, "you came from it, and into it you go." The editor, in a "fugal variation" pens, "Do not despise the future; you go into it, and from you it comes".
Everyone has begun discovering Robert Hugh Benson's long neglected fiction, particularly "Lord of the World" (another sort of futurist novel). Those willing to persevere with Benson may delight in discovering Knox as well; both converts, both Catholic writers.