The latest update of "C++17 - The Complete Guide" now contains a detailed description of the whole new C++17 filesystem library.
by Nico Josuttis
About the extension:
50 pages about all elements, all differences between POSIX/Linux and Windows, many examples, many tricks, traps, and hints as well as what changed with the library when it became part of C++17.
All examples were tested both with Visual C++ and g++.