Where are you from/what's your mother tongue Waikiki? The way I learned English, I focused more on grammar because it was actually easier for me to learn colloquial English. You need to use proper grammar for others to fully understand you and take you more seriously (<--by that I mean I didin't want to sound like a foreigner and people to think that I was somehow not intelligent because of bad grammar).
If you want to learn slangs and everyday conversation type of English, maybe you could get a tutor whose native language is English. And this forum is a pretty good place already to see how people interact in written text
Just a friendly suggestion from my experience, but everyone learns differently so again each to their own and by all means go ahead and read Paris' book.