It looks like an introductory C programming book.

I was hoping for it to be a "hello experienced C programmer, here's new stuff that's happened in the past 20 years" kind of thing which would be useful.

I think most people have a hard time keeping up with the progress of all the technologies they use unless they've got a pretty narrow focus.

For instance, I learned make in the 90s. I should probably go read up on what's happened in the past 25 years or so. Probably lots of cool stuff.

Edit: it looks like just reading the release notes is probably sufficient. There's indeed lots of interesting new things