Yes, it is. Of course, following this sentence up by describing the article in question as "Liberal refusal to accept any evidence that any person ever spied for the Soviet Union..." is lying, but don't let that bother you.
If you can get off your pompous high horse, maybe you could reread post #25. I think poster hits the nail on the head. Some of you guys just refuse to admit you are wrong.
The review could have been more carefully written to indicate (right where the phrase "entirely circumstantial" was used) that it was the case as it happened to have been presented which was circumstantial--and that there was conclusive evidence of Coplon's guilt.
But the review, like the book, took awhile to get around to that point.
So Ann is guilty of jumping the gun on poor writing.
Cheers!