Hey! This is NOT "Murder on the Orient Express" (which was written by Agatha Christie.) But the publisher sure wanted to make you think it was. This book was initially published in 1933, titled "Stamboul Train." But a US publisher picked it up, retitled it, put lots of references to "murder" on the cover, and probably sold a lot of copies.
Nevertheless, this is a very well-written book, although it is more of a study of characters and a discussion of how politics intersects with individuals' lives, than about murder (although there is an element of murder). In 1933, the inclusion of both Jewish and lesbian characters was probably considered quite radical, although to a modern reader, their portrayal will raise some eyebrows.
It's a very interesting book in that it doesn't offer even the hope of anything pure or ideal... but when things turn out the way they do, the reader still feels distraught, even though one can't logically argue that things would have been any better all around if coincidences had gone differently...
vintage 1970 bantam paperback with cool white cover