After previewing, you should have a one sentence summery about what the book is about. Get into a conversation about that one sentence summery. For example, the top book of my syntopic pile is "Natural Brilliance." My one sentence summery of it is, "How to overcome stuck states and find solutions to paradoxical problems." I could start a conversation with you to the effect of, "I've been given a book on Yoga by the books author, and I've had it for over a year, but I've never done the program for more than three days. I have plenty of time, but I keep either forgetting about it, or simply making excuses." (In this case, I am mentioning a stuck state). You might tell me something that activates one of those neural chains. Or, I could mention the whole syntopic pile's summery, "If people are always doing the best their current awareness allows, why does there seem to be an abundance of evil and a deficite of good in the world? What factors are limiting human awareness so much that we are about to start World War III between the Middle East and the Western Empires?"
I find it best to talk about the subject of the book, rather than the contents, especially with syntopic reading. You're almost always going to find someone willing to talk about the subject of a book, even if they've never read it. (e.g. "What do you think about Goldhagan's "Hitler's Willing Executioners?" will give you far less people able to converse with you compared to "What do you think about the idea that the German people were not only aware of the Holocaust, but eager to help out?")