The latest version of Ionic at the time of this book's release is 3. I have put together another chapter named Ionic 3 (Chapter 11), to which you can refer to know more about Ionic 3 and its changes.
Also, please note that the examples in this book are still valid when working with Ionic 3 as well. There may be few syntactic and structural changes, but the overall gist should ideally remain the same.