You will start with learning about the so-called big four Concepts, Coroutines, std::ranges, and modules. The big four a followed by smaller yet not less important features. You will learn about std::format, the new way to format a string in C++. In chapter 6, you will learn about a new operator, the so-called spaceship operator, which makes you write less code.
You then will look at various improvements of the language, ensuring more consistency and reducing surprises. You will learn how lambdas improved in C++20 and what new elements you can now pass as non-type template parameters. Your next stop is the improvements to the STL.
Of course, you will not end this book without learning about what happened in the constexpr-world.