I must say, I was really surprised by this book. Not only it goes a great length to explain things about Angular (the base for Ionic), but builds two applications from start to end, connects to other services and also explains how to publish your application.
But (and there is always a "but") I felt some things lacking. For example, the author says that he prefers to use grunt instead of the default ionic tool, but after that, he only uses the ionic tool; there are some things wrong with the book (why I already submitted as an errata for it); there is very little mention on how to deal with different rotations; and the gravest problem of all, in my opinion: There are absolutely no tests. At all. Not even a mention on how to test your Ionic app.
Other that those problems (which are really minor, related to the amount of information), it is really a good book to start working with Ionic apps.