I suppose I can't be terribly surprised. In general, Golden Age mystery writers tended to decline in ingenuity and all-around cleverness towards the ends of their careers. At least as often as not, this was because of literal cognitive decline- Agatha Christie has now been suspected of having had Alzheimer's by virtue of literary analysis of her final, forgettable Poirot novel (Elephants Can Remember). John Dickson Carr, another great, is also considered to have written his greatest works by 1960. I'm discovering more and more that the same principle applies to Ellery Queen, and A Fine and Private Place is the final Ellery Queen novel. Uh oh.
It's a short trifle of a book- 192 pages with 15-20 of them blank for plot reasons. I read it in a day and a half, which calls to mind Christie more than Queen. So it was breezy enough. But it suffers the faults of Late Queen in large quantities. The cast of characters (and therefore, suspects) is extremely limited. Hard to have a whodunnit when the functional number of "who"s numbers less then four. Anyone with half a brain will have this one solve by the time queen has doled out all of the relevant clues...
As far as it can be figured out. The culprit isn't difficult to discern, but the convolutions of the murder plot just flat out don't make internal sense. And this is really the heartbreaking bit. For writers who, in the first 10-15 books especially, were known for tight chains of deductions, to deliver a plot this broken is quite out of character.
I'm still hoping there are some mid to late Queen gems out there, but for now, the hunt continues unsuccessfully.