This meeting was very helpful - both for the suggestions and the encouragement.
I was just at the point where I was thinking that I should be telling this story completely differently, that the way I was telling the story is too boring at first, and all that sort of negative stuff. But Barry said that at the end of the 20 pages he wanted to read more, and that often when he reads the 20 pages (by other writers asking for his review) he is relieved he doesn't have to read more. He kept telling me not to give up if it takes a while (and many rejections) before selling the novel, which kept me thinking that maybe he really does like Mysterious Paris (and is not just mouthing encouragement).
His suggestions are good, and sometimes touched on my existing concerns. I think some of his most valuable suggestions will be on how to write a plot summary for the query letter (although that won't be for a long time). I wasn't happy with my plot summary, but he explained better what I should try to accomplish.