When you talk about abnormality in behaviors, it is not just about being too violent or being too out-of-reality. Abnormality in behaviours may be as simple as not eating because of obsession in losing weight to as complicated as killing someone just because one would love the feeling of seeing someone dead.
If you really wanna learn more on this stuff, try to read DSM-IV TR. A handbook primarily made to diagnose disorders by means of placing the signs a d symptoms of the disorder on its pages. I find this boring at first but through passing by its pages- it is a worth while stuff to read.
I concede to the fact that a novel by Anne Rice would be better than DSM – IV when it comes to thrilling scenes, but learning wise – absence of DSM in a clinicians life would be a total devastation.
Why am I writing this stuff? I just wanna share something that made my college life nerdy but interesting. 
