Which specific claims from The Bell Curve do you disagree with?
The most contentious point, regarding racial differences in IQ, has been confirmed many times.
It is a 1000+ page book. Many have said more than should have been said about it. My problem with it starts from the premise that IQ measures anything other than the ability to think like the middle class designers of the tests want you to think.
The premise is supported by mountains of evidence that IQ (despite being a crude, one-dimensional measure of intelligence) is predictive of intellectual achievements and economic success, in individuals and populations.
So long as you don't look too close at the data. From the Flinn effect to the fact that IQ tests predict parenatal incomes mich better than future earnings the best thing you can say about the test is that it measures willingness to to arbitrary meaningless tasks for long periods of time. A very good predictor for success in most office jobs.
The Flinn effect has run out of steam. We're starting to creep the other way, as one would predict.