MY EARLIER MENTION of Ray Kurzweil’s new book led people to ask for more. Well, I really want to save specifics for the review — but I’ll note that this book is far more densely documented and closely argued (which is not to say densely written — it’s quite readable) than, say, The Age of Spiritual Machines. In the earlier books, Kurzweil was writing mostly for his fellow geeks (like, er, me); here I think he’s more interested in persuading skeptics.