If Lance Armstrong was an ASP.NET developer, this is the book he'd write. There are many many great ASP.NET books, and it'd be impossible to say that one is the 'best'. But I can say for sure that this book hits the ground running and just takes off from there.
As far as the recommended audience, I think you need a little ASP.NET experience to really appreciate this book (although if you are a total newbie, it's still a superb resource). Everything in here, Everything, is pure gold. Example after Example after Example of just cool stuff, with great implementations, cleary written x25.
There's a lot to ASP.NET and I think you need to read more than a few books before you really 'get' it, but if you are developing professional ASP.NET apps, this book pays for itself by the time you hit page 30.
If you aren't into 'cookbooks' and you want an academic discussion of ASP.NET, then this book isn't for you. However, if you want some great practical examples, you'll fall in love with this book quickly.