I read the book Bell Curve years ago, but I remember the analysis being that the found statistically significant differences between race and IQ. The authors argued that individual differences in IQ within a population are strongly influenced by genetics (heritability estimates around 40–80%). They emphasized that this doesn’t mean IQ is fixed, but that genes play a large role in explaining why individuals differ. Their ultimate policy argument was less about race per se, and more about what society can realistically do. They argued that large-scale social programs (e.g., Head Start, income redistribution, affirmative action) had limited power to reduce cognitive inequality or close gaps, because much of IQ variation was resistant to environmental manipulation. On the genetic vs. environmental debate about group differences, their ultimate claim was: we don’t know, but genetics might contribute, and pretending otherwise could be harmful to honest policy discussion.

But really, if you can't go about doing more studies on race and IQ, we'll never really know. It's a valid and legitimate scientific question

This is an extremely studied question, and The Bell Curve operates in the phlogiston era of this science. The idea that this is a forbidden topic only whispered about in the academy is an Internet myth.

Most of the reason you don't hear about current research into behavioral genetics is that a, uh, very particular excitable subset of Internet commenters are actually interested in this research, and the research results aren't coming out the way they want them to.

(You can get an isomorphic answer substituting psychometrics for behavioral genetics; this is the "twin studies" line of research that Richard Herrnstein relied on in the book, and it too is actively studied, but not talked about because the answers don't come out the way --- let's call them "Herrnstein fans" --- want them to).