Broca's brain is a difficult book to rate, because Sagan is really all over the place with it, covering tons of different topics. I gave it four stars because a lot of it is fascinating and amazingly written (easily 5 stars), but some of the other sections really pull it down. By and large, it's all good stuff, with two exceptions - he goes on for a couple dozen pages about the names of various craters on various planets and moons in our solar system. Maybe I missed the point, but I just couldn't get interested in it. The second thing, which is what really lost the book that last star, is the chapter on Velikovskian Catastrophism. Apparently around the time this book was written (about thirty years ago, but it's all still interesting and relevant information), there was a book going around by someone named Velikovsky, who pretty much claimed that the book of Exodus, and all of the fantastic things that happen in it (the plagues, the parting of the red sea, etc.) where caused by some six comets or meteors that passed so close to the earth as to gravitationally (or magnetically, apparently this Velikovsky isn't quite sure) affect various things (i.e. somehow the gravitational pull of the nearby comet caused the water of the red sea to rise up in two different directions, therefor allowing the israelites to pass in between). Now I have a great deal of respect for Carl Sagan and his work, and I don't know what the climate of popular science was like thirty years ago. Clearly he felt a need to strongly discredit this theory - maybe a lot of people believed it then. But today, it seems pretty silly - I'm not a student of physics, astronomy or anything like that and the sum of my knowledge on the subject comes from popular science books that I enjoy reading. But the idea of six meteors flying that close to the earth, over the course of a couple months, plus the effects that Velikovsky claims would result, seem completely impossible - requiring maybe a page or two to respectfully discredit, but definitely not the fifty or so pages that Sagan uses to completely (and, it's important to note, respectfully) demolish the theory. I found it very tedious. I know that I've gone on for a while on this, but it really bothered me and detracted from an otherwise excellent book. Also highly recommended is Dragons of Eden, also by Sagan.