Death of a Queen by Christopher St John Sprigg is definitely a Forgotten Book. I've been searching for it in vain for many years, but I finally had an opportunity to read the British Library's copy. If you found a nice copy in a dust jacket, it would be a good investment, I suspect, because the BL's republication of Sprigg's Death of an Airman has led to a renewal of interest in this fascinating author. Some people have told me that book is their favourite in the Crime Classics series.
Published in 1935, this was the last conventional whodunit to appear under Sprigg's name prior to his untimely death in the Spanish Civil War. (Six Queer Things was published posthumously). The book is sub-titled "Charles Venables' fourth case", and here the journalist is called upon by Whitehall to assist a sympathetic (and conveniently English-speaking) tiny state in the Balkans.
My heart sank when I realised that this story takes place in Iconia. So many Golden Age books have plots or sub-plots involving sub-Ruritanian kingdoms on the brink of revolution, and handle the material ineptly. But Sprigg recognises the difficulties, and explicitly, if rather cheekily, makes it clear at the outset that Iconia is no Ruritania. He also invents the country's history, heritage and architecture with great enthusiasm, and this makes the story all the more appealing.
What's more, there is a very good "impossible crime" at the heart of the story. How did the eponymous monarch - strangled with a silken cord - meet her end, when her chamber was under constant observation, and nobody saw the murderer go in or out? Sprigg handles the unlikely plot twists with gusto. All in all, this is an enjoyable story, extremely far-fetched, but told with youthful zest. I'm glad I overcame my initial reservations and read it through to the end.