I bought this book in Idaho Falls on my way to a camping/biking vacation. That was a few years ago.
This is a very slim book, but there is a lot of information about the latest scientific findings related to the pleasure circuits in our brains (and the brains of mice, rats, and various monkeys).
It turns out that all of the drugs that we know and love, like heroin, cocaine, nicotine, THC, caffeine, and speed, directly affect the pleasure centers of our brain. And depending on how these drugs are ingested and how often, they can rewire your pleasure circuits in a way that you become addicted to them.
No matter the drug, addiction follows a pretty standard progression: pleasure, increased tolerance, craving, withdrawal, and (usually) relapse. In this book Dr. Linden sketches out the insights into the physiology of these stages. The tools used to measure the brain are pretty crude (and horrifying if you are a lab animal), but the first glimpses of how this part of the brain works are starting to come into focus.
But the book isn't really about addiction; it's about stuff that humans and lab animals like to do. This includes eating (of course), having sex, socializing (except for me), and gambling. It ends with a look at some surprising things that activate the pleasure center of the brain like donating money and even abstract ideas.
This book gave me plenty to chew on. I'm reading his other book now, The Accidental Brain.
I'm unsure how accessible this book is to "lay" readers. I don't have much biology or chemistry background, so I was a little lost when he would toss out the names of specific areas of the brain or specific neurotransmitters. You can still get the gist of what is happening, and there is an index if you need to go back to reread something. It's probably best to read this with some postit notes on the inside cover and a pen in hand.