This book has been much-summarized and over-quoted. Many nuggets that inspire thought. Even more buzz words. Basically: the best way to build an addictive product is to solve a problem for the user whom you know best—yourself. Make the product so intuitive to use that it inspires investment. We overvalue our own work, so the more we invest, the higher the barrier to switching. Create variability in the level of reward—sometimes the user gets rewarded, other times he doesn’t. And he’s hooked. Hopefully the product is designed for good (and not for evil), since you now have a bunch of addicts on your hands.