After years of reading about "The Bell Curve" (including Stephen Jay Gould's critical New Yorker article), I finally got around to reading the book itself. I read the whole thing, including all the appendixes. It's clear that what people were so worked up about was not what this book says, but what they *thought* it says. What's the reality?
1. The book is very measured in its analyses and tentative in its conclusions.
2. Group differences in IQ are only one topic discussed, and far from the main topic.
3. The authors agree that the extent to which IQ is heritable is unknown. Their guess is 60%, but they make clear that that's only a guess. They also point out that even if IQ is 0% heritable, that wouldn't change that fact that people show IQ differences very early in life and so far no intervention program has been found capable of bringing about large, sustained IQ increases.
4. The authors also agree that early intervention might be able to close the black-white IQ gap, although the results so far have not been very promising.
It should also be noted that the American Psychological Association devoted an entire issue of its main journal to many of the foundational questions discussed in "The Bell Curve" and expressed agreement with Herrnstein and Murray's conclusions on those questions. (A summary of the APA's report was published in the Wall Street Journal and can be found on the Internet.)
Finally, it's also worth noting that in 2001, Oxford published "Intelligence" in its excellent "Very Short Introduction" series. That volume, by British psychologist Ian Deary, cites "The Bell Curve" several times as recommended reading. If you want to learn more about intelligence research but don't want to tackle "The Bell Curve," Deary's book would be a great choice (and it's worth reading in any event).
On the con side, Thomas Sowell's article on "The Bell Curve" is the best thing to read. (You can find it on the Internet.)