The Hitchcock/Truffaut book,which is actually a very long interview ,something like "the Beatles anthology" in pop music ,gives us many interesting informations about "Mary" ,a movie the master liked.Although he told Truffaut he detested the whodunits ,those riddles a la Agatha Christie,"Mary" featured "things we did for the first time":stream of consciousness,play in the play a la "Hamlet" references to transvestism and even hints at (veiled) homosexuality,which was a "crime" in Great Britain as it was in Germany at the time....
That said,the story drags on a bit and the running time could have been boiled down to one hour,which would have enhanced the really good scenes: IT was Herbert Marshall's first talkie and the scene when he's shaving and thinking for a clue renews the way the detective investigates.The unfinished manuscript is also a very good idea.But the bravura passage remains the final circus.One can also note the scene of the verdict we hear from the empty juror's room.
There are elements which would appear later in Hitchcock's work: the theater ("Stage fright",also a whodunit,btw),of course "Psycho" (a man in drag) and "vertigo" (the finale which makes you feel dizzy).
This is another early Hitchcock which is not only for completists.
