How to start learning Asp.Net MVC ??

I have been developing .NET (web application) for two years and want to learn MVC.
1. Can anyone suggest best way to start or what step i have to take to learn from basic example and which reliable resources to use?
2. As MVC has MVC2, MVC3, MVC4 so on versions, Do i need to learn all of them??
3. Which book is good for beginners??

please suggest.