Books to learn FreeBSD structure

I'm thinking on buy a book to learn intern structure of freebsd, in other old thread i did see that recommend some books like:

My questions are:

Are the information in these books still more or less current to learn?
Any book in Spanish?

Also try Kong's newer book on FreeBSD device drivers. I have been reading this and it seems great! Kong makes a lot of effort to explain things, and whatever he omits is fun to figure out on your own :).