What's a good book or various resources to understand the internals of Linux networking?

I'm not looking for a book that explains how to administer a Linux network.

So far the book I found is called understanding Linux network internals by Christian Benvenuti. The only problem is that this book was released in 2005 and it might be out of date.

Can I still use this to understand this topic even though it's 16 years old? Back then the latest Linux version was 2.6.11. Today it's 5.12.12.

But if the theory was out of date then surely a new version would have been released?