The hollow man (1935)

Dr Gideon Fell faces a vanished visitor and a murder whose apparent physical limits refuse to add up. Carr gives the reader substantial material for testing boundaries, witness statements and alternative explanations. The discussion of impossible crimes is part of the book's attraction, but also a sign that it is prepared to pause and theorise. A demanding choice for readers who enjoy reasoning about a puzzle's construction. Also published as The Three Coffins.