Josephine Tey's The Daughter of Time, as to which much ink has been spilt on the pages of book blogs, often gets in the way of understanding that she was also a legitimate Golden Age crinme writer, though nowadays sadly neglected.
In this book her Inspector Grant, one of my favourite fictoinal detectives, faces what appears at first an intractable case. A man is found to have been fatally stabbed while in the queue for theatre tickets. The corpse held upright by the press of bodies, his killer has long since had a chance to slip away, and even the identity of the dead man is not known.
Grant is an intensely credible detective, very much an everday creation, much more of a Wycliff than, say, a Campion or even an Alleyn. Success usually comes as much from dogged police procedural work as it does from Grant's instinctive hunches which, incidentally, he freely admits are usually wrong. The French have a name for this sort of book, a policier, and Simenon's Maigret books are probably the best example.
Though this book was first written as long ago as 1929 it is remarkably undated, and I recommend a perusal of Tey's ouevre to anyone interested in the detective novel as a genre.
Incidentally, even though it is not intended to form any part of the subject of this post, I should state for the record that I personally find The Daughter of Time an excellent book, though I can think instantly of at least one book-blogger who would give me a fierce argument on this!