The best place to master c++ is StackOverflow. Many people share knowledge accumulated from experience and they explain much better than Herb Sutter or any gray beard people in C++ community.
Another important thing, no matter how many books you read, you can't be a master without actually solving a lot of problems.
SO is a great resource but it's about as good a place to learn something as Wikipedia is to do serious research.
Questions from learners are often poorly formulated and then poorly answered. Since many people are just looking for getting their code to run or finishing their homework, this sort of stuff just piles up without getting fixed.
If you're trying to learn anything non-trivial, don't rely on SO alone.
SO launched a new feature recently called Documentation. Check out the C++ section [1]. Personally, I'm enjoying it a lot. I think they managed to find a very concise way of showing the basic grips of a language and some advanced ones. Most stuff are through examples, which I think works better when you're already familiar with the language, and just wants to do some specific thing. From time to time, I find myself on the page surfing through the C++ topics.
There is a lot of wrong and dangerous advice on Stack Overflow about C++. I also disagree that it is good as a learning tool. The C++ Annotations book linked to will much better place to master C++. As it turns out, 'gray beard people in the C++ community' actually know the intricacies of the language, and you better learn them too otherwise you're never going to be productive with it.
Another important thing, no matter how many books you read, you can't be a master without actually solving a lot of problems.