There is 2 types of dependence associated with drug abuse. Physical dependence and psychological dependence. They usually both work hand in hand but depending on the drug determines how much. Most drugs of severe abuse potential cause a strong physical dependence, like heroin. You find a stronger psychological dependence with drugs like THC(cannabis). Another factor in drug abuse is an individuals mental health where someone is self medicating through recreational drug use that leads to addiction.

Probably one of the best all around books for a laymen about drug use and abuse is "From Chocolate to Morphine" at least the edition I read back in the 90s. I don't know if it has been updated or revised and the PC Nazi's had it changed but it was a good reference for discussing different classes of drugs, their affects and which methods of taking the drugs have the highest risk of dependencies to those drugs(Like injestion, smoking, snorting , and injecting the drugs). When I had read it I always thought it should have been a companion reference to a sane drug education/awareness course for young people who are at a high risk age for experimentation. It offered some very straight forward information that assumes you are going to experiment rather than just tell you to abstain.

http://www.amazon.com/Chocolate-Morphine-Everything-About-Mind-Altering/dp/0395911524