Even if I am an advanced ASP.NET developer, I learned very much in this book. This is not so common these days.
You probably think as I did that writing mobile application with ASP.NET is the same as to write ordinary ASP.NET applications. Much is the same, but some things are rather different. Even if ASP.NET helps you with the different devices, in advanced applications you soon have to work with them yourself. (By the way, they haven't to be so advanced before you have to take this into account.)
This book, "Building Microsoft ASP.NET Application for Mobile Devices, Second Edition", helps you with that. It is a good book to have as reference literature on your desk when working with this type of applications.