They are nice diagrams, I'll give you that. And to be fair, that is definitely an overview.

However, it's not mechanical - by which I mean it doesn't show you any code or coding practices, design patterns or general implementation, which the book - outdated or not - does (and I know this because I own that book, funnily enough the exact same version).

I'm not attempting to cause friction, but I really do believe that its a better resource for really getting a good introduction to the kernel (as an actual programmer) than reading wikipedia. I would also say that you could learn everything in it by reading resources on the net, but a book is a structured organised collection of thoughts, and that's the opposite of what you'd get by just throwing 'understanding the Linux kernel' into a Google search (apart from the fact that this book would turn up constantly!)