As I read through this book I didn't understand anything of what it was talking about. I suppose the main reason for that is due to Paypal introducing a number of new ways of integrating Paypal into your web site over the past few years. Since the IPN script that I wrote some years ago provides all of the integration that I and those who buy the script need and many of the new features that Paypal offers are only available in some countries, I haven't really looked all that closely at the newer offerings from Paypal.
I suppose another reason that I couldn't follow the book at all is that upon trying to find IPN in the index (since that was the first way that Paypal offered for integrating Paypal into a web site and appears to me to still be the most obvious approach for many situations - particularly those involving electronic goods) and discovered that there is no reference to IPN in the index at all.
The first thing the book talks about is obtaining API credentials in order to be able to use the APIs that the book covers. It then discusses Paypal Express Checkout, Paypal Website Payments Pro, Paypal Adaptive Payments, and Paypal Mobile Express Checkout. While I have seen some of these referenced in forums, I have never received an email from Paypal that mentions any of these and have never seen any of them mentioned on any of the pages when I log into my Paypal account. The only new service that Paypal has emailed me about is one allowing credit card payments to be taken over the phone and the book makes no mention of that. That I have no idea what any of these facilities the book covers are probably also helps explain why I have no idea what any of the content of the book is talking about.
From what I can see from what is in the book these Paypal facilities look like they relate to shopping carts and so if your web site uses a shopping cart and you live somewhere that Paypal offer these facilities and you expect that your customers will also all live in an area where these facilities will work then you might be able to make some sense of the book once you have figured out what the Paypal facility is all about.
On the other hand if you don't have a shopping cart and just want to sell single products then you don't need any scripts whatsoever if what you are selling is physical goods. Also if you are selling digital goods individually then a simple IPN script that emails the files to the buyer once their payment clears still appears to me to be the simplest way of handling things.In either of these instances there is nothing of benefit in the book for you at all since as well as not mentioning IPN in the index there is also no mention of either email or delivery and so I can only presume that the book is only dealing with ways of simplifying the checkout process for shopping carts that involve physical goods.
So the book is basically all about shopping carts and some of the new features that Paypal have made available in some areas that allow the payment process for people in those areas to be streamlined.
I am not going to attempt to give this book a ranking the way that I do when I usually review a book because in the right circumstances the book may be just exactly what you need. The book is targetted at a specific small group of Paypal users who do need the sorts of facilities that the book covers. The only failing of the book in that regard is that it isn't necessarily obvious until you see the book as to whether or not you are in that target group. Hopefully this review will assist you in determining whether the book might be applicable to your circumstances.