An answer to this can be gleaned from the Books, etc. summary page on Scott Meyers' website:
Effective C++, Third Edition, 2005. Scott's flagship book, and the
industry's must-read second book on C++ (i.e., what you read after
you've learned the fundamentals of the language)
Read this first.
More Effective C++, 1996. Still relevant after nearly 20 years!
Indispensable in its own right, and an invaluable companion to
Effective C++
Read this together with, or after, Effective C++.
Effective Modern C++, 2014. The book on effective use of the features
new in “modern” C++ (i.e., C++11 and C++14). A complement to Scott’s
existing books
Read this once you have mastered the concepts in the other two, as it is focused on the changes in the later versions of the language.
Effective STL, 2001. 50 specific ways to improve your use of the STL,
including techniques for improving performance, eliminating resource
leaks, avoiding portability problems, and more — all in Scott's
inimitable style
This one is less clear although I would suggest reading it after the first two and before the third.
