We see that Mr. Canada and his brothers were raised by their mother in the tough projects of the Bronx in the late sixties and early seventies. Sadly many of the social ills he describes are still prevalent today and in some cases are even more pronounced.
In tough neighborhoods there is a code of the streets that must be learned in order to survive and Canada describes how his mother often let he and his brothers make mistake in order to learn from them. As the boys mature, Canada describes various older male figures that "showed him the ropes" so to speak in terms of fist fighting and wielding weapons.
The lesson that I think can be gleaned from this book is that though conditions may be tough in one's life, it is up to you to try as best as you can to transcend your surroundings and make a better life for yourself. Canada ultimately rejected the gang lifestyle and has chosen to create educational opportunities for residents of the very neighborhoods where he once lived.