This book is for developers who know their way around C# and Visual Studio. You don't have to be a professional programmer, but you should have basic knowledge of object-oriented programming using .NET and C#. The typical reader would be someone who wants to explore how you can use Xamarin, and specifically Xamarin.Forms, to create applications using .NET and C#.
No knowledge of Xamarin is required in advance, but it would be a great help if you've worked in traditional Xamarin and want to take the step toward Xamarin.Forms.