You won't learn anything from Ubuntu, or CentOS. Read up on the way linux really works ... not the Windows copycat version of Linux.
http://rute.2038bug.com/index.html.gz
Best book/manual written on linux to date. You can also buy it in dead tree form if you want.
Worst advice ever. Not only did I learn most of what's in that book despite the fact that I use what you call "Windows copycat version of Linux" where "you won't learn anything", moreover I can assure you that nobody on the face of the planet, except maybe the author of the book himself, wants to learn ANYTHING from a book whose first chapter has a subsection "1.5 I Get Frustrated with UNIX Documentation That I Don't Understand". I hadn't even finished reading the table of contents, and already I feel patronized.
IMHO, this book was written by a *nix-ier-than-thou elitist chump, which you can see just by looking at chapter 6 -- It's all about Vim, with only passing mention of emacs, based on the assumption that you're gonna want to do everything just like the author; that is, with your head up your ass. Chapter 3, on hardware, belies his recurring attempts to over-explain EVERYTHING down to the barest low-level and inundate the reader with specifics that were probably copied straight out of Unix MAN pages, and on that note, his stupid domain name is a joke about a time overflow bug that nobody's ever heard of, and will not hear of for at least 25 more years.
I'm not saying that there's not a lot of good information in that link -- In fact, it seems like he covers at least 80% of my basic day-to-day programs and workflow. I just wouldn't want to "learn" it from that guy.
Disclaimer: Woke up with a stick up my ass today, to be blunt.