This is a story of one very unusual and several fairly interesting characters - no more and no less. Some reviews talk about how well the film captures the look and feel of 1940 New York, but Tucci kindly does not hit you over the head with atmosphere; there are no "do you get it? You realize who that was supposed to be?" scenes. Instead he merely nails down the milieu so precisely that it becomes unobtrusive, and allows you to focus entirely on the characters and their story. Likewise he seems to ignore who in the cast is a star, in favor of who is right for each role. The result is not quite a touching story, nor an inspiring one, nor a tragic one, but a satisfyingly believable as well as intriguing one. Not a documentary, by any means - it is far more creative than that - but fine story-telling. No individual and no event is larger than life, but all are handled with respect and just enough affection. The fact that the story is true is almost incidental; from what I can tell, memorable characters such as Harold Ross (and of course Gould) are portrayed with great accuracy, but what really counts is that they work as characters.
Don't worry about what the secret is. Just get to know these people. You'll like them.
Don't worry about what the secret is. Just get to know these people. You'll like them.