Rating: 3/4 (Recommended for the bookshelf of any STL user)
I find myself using STL a lot in my C++ code. I also found that I was continuously rewriting the STL code, every time I discovered subtle bugs in the way I was using it or when I found a more elegant solution to the same problem. Looking around for wisdom on STL, I picked up Effective STL by Scott Meyers. Scott has authored two other books: Effective C++ and More Effective C++, both of which I have found to be approachable and useful.
Like the other books in the Effective series, this one too has 5x chapters or items, as they are called. The topics they deal with include containers, iterators, algorithms and functors. The whole area of extending STL has been skipped and left for other books. Each item in the book is self contained with a title, introduction, examples, explanations, guidelines and sometimes even trivia. I found the book very useful, showing up mistakes in my code and also sharing a lot of idiomatic methods to write what I wanted. While reading the book, I found myself compelled to go back to my code and start polishing it immediately! Much like the other Effective books by Meyers, Effective STL too is really easy to read, understand and apply. Recommended for the bookshelf of everyone who uses STL.
Related: My notes from this book can be found here.