How can someone be so close to the right answer yet so far at the same time?
The book per se is not wrong, but it ain't right either.
While Bonger clearly says that race ain't a factor for criminality, he also doesn't explain how certain cultural groups commit more crimes than others (and, surprisingly, he seems to forget all the marxist theory he exposed in his previous book).
There can only be two explainations (and each one is as tragic as the other):
1.- Bonger was secretly a racist and couldn't accept that the material conditions from marginalized groups are what force the people to participate in illicit activities. Or in other words, that the criminality of certain social groups are the product of the capitalist mode of production and its history manifested through racism, discrimination, unequal wealth, unpaid labour-exploitation, slavery, etc.
or
2.- Bonger didn't understood marxist theory and couldn't come with a reasonable explaination.