I am a beginner for WCF and I would like to know which is the best practice book for WCF
I personally found:
Programming WCF Services by Juval Lowy
to be a very good book.
It's not necessarily a "beginner" book, but if you have even a passing familiarity with such things as web services or .NET remoting, you shouldn't have any problem. For example, when I read the book, I had experience with "standard" web services, but was a complete "beginner" when I came to WCF. I found it to be very helpful in both initially explaining WCF, and also being a "reference" book. Something to keep on your desk and refer back to as you're developing applications using WCF.
The book has been recently updated (the link above is for the 3rd edition of the title), however, I actually read the previous (2nd) edition of the book. I'm assuming the content hasn't changed too drastically. As a bonus, this new edition includes content regarding accessing and consuming services based upon Azure AppFabric Service Bus, Microsoft's "services-in-the-cloud" offering.
If you're only just starting to do web services in ASP.NET, I would strongly recommend you go and check out WCF. It's the current and future standard for communications between machines - web services and a lot more.
The book I always recommend to get up and running in WCF quickly is Learning WCF by Michele Leroux Bustamante. She covers all the necessary topics, and in a very understandable and approachable way. This will teach you everything - basics, intermediate topics, security, transaction control and so forth - that you need to know to write high quality, useful WCF services.
The more advanced topics and more in-depth look at WCF will be covered by Programming WCF Services by Juval Lowy. He really dives into all technical details and topics and presents "the bible" for WCF programming. He just recently completed a third edition, which covers WCF in .NET 4 and AppFabric and the Azure Service Bus, too.