It is an excellent book and an important one from a historical point of view.
Note that to implement the practices described in the book, you need considerable discipline and agreement within the team. Here are a few things to note:
Lakos has precise definitions for what he calls "components" and "packages". These are key for large scale design. However, they require adherence to conventions for how source and header files are named and the sequence in which they are included. It is a shame that most people (including those who quote Lakos) rarely follow these conventions.
The book is all about C++ but the concepts are more widely applicable. However, because C++ is such a complex language, a large part of the book is teaching you how to use C++ effectively. If you can get past that, you can actually find it useful even if you use other languages.
Some of the prescriptions such as on the use of "name spaces" maybe considered controversial now. Many believe that name spaces should be used in a limited way in C++.
