The C++11 standard was a revolution in the language. It made C++ a new language.
The C++20 standard is the most influental standard since C++11, it has a ton of new features.
The book has 530 (!) pages and describes the new features, therefore the book explains the difference between C++17 and C++20. Despite the book’s size, it is not bloated🚱, everything written there is important, it has the most detailed explanations and code examples.
It can be feeled that a huge amount of work has been put into the book. Almost all things are explained better than “on the Internet” (on cppreference.com and similar sites). As for “big” features, their design history and other rare information are described.
The book can be read as a reference book - a chapter at a time. Some features, unfortunately, are not yet supported normally by compilers (as modules), or rarely used (as coroutines), so it’s worth remembering that rarely used features are quickly forgotten.