[SLL] Good Red Hat book?

[Glenn Stone]

I have on my hands a reasonably experienced Windows guy who's being dragged
not protesting too badly into the 21st century, and needs to learn Red Hat.
He wants a good book.  Alas, having picked all this up in fora like this, I
haven't a clue where to send him.  Recommendations?  

(And if you happen to have something similar for AIX, that wouldn't go amiss
either.)  

Thanks,
Glenn