Alan Carr's Easy Way to Quit smoking for me. 10 months now and it really was quit easy after being on Marlboro Reds for 10 years. Started reading it after a thread on Reddit with no real intention to quit, smoked throughout (as he recommends) then was convinced to stop when I finished the book. It's a little cheesy/self-helpy but it's short and worth giving a shot and taking seriously. I immediately felt free when I stubbed my last cig.