What are the best book to learn C#?
O'Reilly Media is publishing a lot of books about all kinds of topics and they have some good C# titles.
Sams Publishing | InformIT also makes plenty of good books.
WROX also has a very good reputation for books.
The above three publishers are the big names for books, especially for Windows and C#. If you're in a bookstore, search for these three publishers and check the contents of each book to see if it is worth buying.
It is difficult to advise you a book without knowing your experience and background. The whole C# is a huge development platform. I could advise you a book about C# which does a lot with WPF, but if you want to develop web applications, that book would be useless to you.
You can also buy books from Microsoft Press at Programming | Microsoft Press Store, for example. Here too, you would find some good books, mostly exclusive to Microsoft technology. Filter on C# and again, you will find lots of useful titles.
Which brings me to another point. Which version of C# will you be using. Assuming you want to use the latest version, you will have to check the publishing date for each book, since they can become obsolete real fast. For example, I have books about Silverlight, but that's obsolete. Silverlight is deprecated. The same will be true for other techniques discussed in these books. So check the publishing date for each book. Anything printed in 2016 will be more up to date than books published in 2015. And books published before 2015 will not mention Visual Studio 2015 so again, those would be a bit old.
Second, third and even higher editions indicate that a book was worth updating so it was likely popular enough. It also means that you will have some older material mixed with new and updated material. That's actually a good thing if you're going to maintain existing projects but if you just want to build new projects, you have more value in books that are newer.
Also check the version number of C# in the books. I have e.g. "Essential C# 4.0" by Mark Michaelis but as the name says: it is for C# version 4. Today, we have version 5 that added asynchronous methods and caller info attributes. And there's version 6 which has a small list of new features. And version 7 is now accepting proposals but won't take long before that will be the latest version. (Probably once you've read the book!) (It's a big book!)
If you want to keep track of the latest then Michaelis book isn't the best one. It is already outdated! And that's the biggest problem with books about C#. They can be the best ones today, but next year, they might be outdated and 5 years from now, they're obsolete...
So no, I can't advise you if you want advise about which book to buy.