A lot of the key C++ books in my library are outdated as far as C++11 or 14, but still are pretty valuable especially for legacy code bases. Here are a few good ones that I haven't seen mentioned elsewhere in the thread.
- Sutter's Exceptional C++ books
- Dewhurst's C++ Common Knowledge and C++ Gotchas are useful.
- Sutter/Alexandrescu's "C++ Coding Standards" is good, too.