This is a work by British authors. It's a conservative text, or at least it would be considered research with a conservative bent, today. The authors point out that as late as 1950, nearly 50% of the British population lived in poverty, and there was very little crime. As poverty rates were dropping, to around a low of 10% by the mid 70's, crime rates increased exponentially.
This work, in other words, would be 'a bigot and racist's wet dream'. It is a work, however, that likely holds more truth than most books about criminality. It's been quite a long time since I've read this work so my review isn't very complete. One thing that's true today that was also true in 1950 is that being poor makes it more likely you'll commit crime.