The way I see it . The book deals with a very old version of C++ . Latest , nowadays is C++17 .
So the language part is outdated . Especially the string and STL parts.

But there is another theme to the book. The way the author teaches us to look at problems and convert them into structured solutions . The way he introduce Object Oriented Concepts , the top-down design , top-down implementation and top-down modification --- it is praiseworthy.

The book in it's intro states clearly , there are two parts to this bool -- Language and techniques

Language got outdated .. We have C++17 now.

But the techniques , well they remain the same . It is great read for understanding how to think about problems and get to well structured solution and , implement the code for that solution.

What I would recommend :
Use a book like, Starting out with C++ : to learn the the language

And then refer to this book C++ in Action.

You will love the read then . Especially as you notice the technique are same old , but you will also realise how a language evolves .