I have not read this book per se, but I have tried positive parenting techniques. What I have found is that these techniques--especially reflecting on the outcomes of one's actions and the effects on the child or or others--work best beforehand, not after the fact.
For example, when my son was younger, and we were out at a restaurant, he'd sometimes say "I want to run". I would then ask "Well, do you think that's a safe thing to do here?" or "What do you think would happen?" We would talk about how he could cause an accident or make a server drop the meals because this is someone's workspace, not a running-around place.
You can reflect on outcomes after the fact, esp. negative ones, but at this point, I find it harder to treat negative outcomes as a "positive". The authoritative parent is gentle AND firm, and for me, I need my son to know that there are limits. For example, if he chose to run in the restaurant after our discussion, we would leave immediately, even if it meant me sitting in the car with him while our food was boxed up to take home. Playful Parenting is much the same way; you can do the playful strategy before the line is crossed; after that, you need to stick to the consequences/boundaries you already have.
A lot of what is 'positive' is about the technique, and not necessarily if the child feels it is 'positive'. Giving either/or choices is a good idea at this age (My son is five and makes lots of noises right now: "You can make that sound in your room or you can be quiet out here"). We can rephrase some of the wishful-thinking lies we hear "Oh, you really wish X happened, don't you? That sounds like fun. What else do you wish?" (instead of busting them for lies-- but only when appropriate).
I think Positive Parenting is like any other philosophy-- it should be one tool in the parenting toolbox. I've worked with kids for a long time and there is not One Single Philosophy which I have found to be universally useful. I have to have a LOT of different skills, techniques and responses as a parent (and preschool teacher) because each child will respond differently. Overall, though, I think this technique/philosophy is very valuable to add to that toolbox. :) Good luck to you!