Cheesebaron (3) [Avatar] Offline
Page 68, note about HttpClient: You don't need to use any NuGet to get HttpClient in either PCL or any type of Xamarin project. For application projects, simply import System.Net.Http. In a PCL the profile dictates whether you have HttpClient in the subset or not. Usually for any PCL including Xamarin targets it will be there.

SQLite-net, it is important that when using it on Android, a package with Android N support is picked. There were changes to Android, where you are not allowed to use Android's .so files, so you need to provide your own. There are some NuGet's which still don't do this.

Page 68, abstracting the web service is a good choice, but I would like there would be an argument as to why you would do that, except for being able to mock it. Maybe, you could explain why you would want to mock it and not do an actual integration test against the web service.

Page 74, not sure if you should note that most frameworks use CallerMemberAttribute for the RaisePropertyChanged.

Page 83, maybe introduce ValueConverters, now that you have covered INotifyPropertyChanged and INotifyCollectionChanged. There is the IValueConveter to cover here too or at least mention you are talking about it on page 89.