The Case is Altered, written by William Plomer and first published in 1932, certainly qualifies as a Forgotten Book, but at the time of its original appearance, it was much admired. Plomer, in his late twenties,had moved from South Africa to London, and this was his third novel. His debut, Turbot Wolfe, was a popular story about inter-racial relationships, and he had become friendly with Leonard and Virginia Woolf, who published and promoted this novel with great enthusiasm.
It's a story about a murder, and was closely based on a real life crime. What is unique about it is that the crime in question occurred, in 1929, in the house in Bayswater where Plomer was living. James Achew murdered his partner, Sybil da Costa, in front of their small child. Achew was insanely jealous (and was ultimately reprieved from execution). He dreaded the thought that Sybil might be seduced by any man - including Plomer who (most authorities seem to agree) was gay. In the book, Achew (who is given the name James Starr) is represented by Paul Fernandez, whose attractive partner runs a boarding house; the lodgers include a young man called Alston who is, in part, based on Plomer.
Yet although this novel concerns a murder, it is first and foremost a study of the changing nature of London life and society, with particular emphasis on changes in the class system and political thinking. I found all this historically fascinating, and even though much of the political stuff is naive (contributing to a surprisingly weak ending) Plomer's liberal attitudes towards racial tensions are noteworthy. He portrays the relationships between occupants of the house in Cambodia Crescent, and people close to them, with a good deal of subtlety, and the gay and lesbian subtexts are also interesting.
In many ways, this book reminded me of the work of Patrick Hamilton - notably Hangover Square. It's not a "mystery", and it's clear that Plomer struggled with the notion of plot, but it's really well written and still highly readable. Oddly, Plomer never developed as a novelist, but he wrote libretti for Benjamin Britten and had a perhaps surprisingly warm relationship with a very different writer for whom he became editor, Ian Fleming. Fleming even dedicated Goldfinger to him. Quite something to have on your CV.