The two novellas of Black Orchids have contrasting flaws which keep the volume from being the best of the best of Nero Wolfe, but they're different flaws, so you never quite get tired enough of them to be annoyed.  In the titular novella, the cast of characters never gets enough individualized time on screen or even in the spotlight to be more than just a collection of names.  In the second novella, "Cordially Invited to Death", the long slack time before the first murder and the long slack time afterwards robs the story of any real urgency.  Conversely, the first novella really crackles with Archie investigative work and the second involves Archie and the police dragging Wolfe into investigating something he has no interest in - always a pleasure.  Overall, the book makes a strong case that the novella is an ideal length for a detective story... but perhaps the flaws should give us pause.