Maybe you could install Fedora. It is supposed to be the testing ground for some RHEL innovations. It includes more packages that may be useful for a new user - especially on a desktop; and it has more users who are likely to experiment with some obscure configurations and have a bit of time to help you..

If you are curious, back in the day RedHat released binary releases on ftp. Later they declared that they have changed their mind about desktops, stopped releasing RedHat binary distribution to non-customers (although they release sources for everyone to use, which is what CentOS uses) and to give some migration option to desktop users created Fedora as a mostly independent distribution. Fedora is a self-governed distribution, and so there are things that are slightly different between Fedora and RedHat/CentOS; of course, they are quite similar in most things (the fact that some core Fedora developers are RedHat employees has something to do with it, of course).

If you want to work towards an RHCE, then start with RedHat Enterprise (RHEL) or CentOS---don't bother with Ubuntu or any other distro.

There are books everywhere....I would start with your local bookstore, or the OReilly website. OReilly has quite a few of their books available free online.

But the only way to learn Linux is to install it and start using it.

OK. So if I am planning to learn Centos directly, then which book should I read? Any linux book will do or that should be of centos only? Any book you know?

You can buy RHCE books, but that would give you limited knowledge related to the certification exam and how to pass it. You could try some book store near and find look out for books that cater to Red Hat Linux.
There are books from RH press as well.

@OP: see the list in my post #4

When I started learning I started with CentOS managing a web server. CentOS is really easy. I thought Ubuntu was little harder than CentOS probably because I start with CentOS. So I think CentOS and Ubuntu are both easy to learn. However Ubuntu makes a better desktop and CentOS in my opinion makes a better server

Thank You everyone for your input...Im really grateful to join this community and gain knowledge over here..So I Have decided to download the centOS and continue with learning that...but one more doubt..
Should I buy books relating to CentOS only or I can buy any Linux book? Basic linux book and CentOS books are completely different?

CentOS is a great distribution it is very easy and install with YUM (Yellowdog Updater Modified) will make it easy install software. I would recommend getting a book for reference but all the documentation you need is online as well. I use The Complete Reference Linux Sixth Edition and Linux Unleashed.

For CentOS Specifics read documents here http://centos.org.

Good luck with your new linux system

At the heart, most of the Linux distributions would be same as they use Linux kernel. So for learning basic commands any book should most probably help you out. But if you are taking certification exam I would definitely recommend a book that is solely written for RH or CentOS. It does not matter. CentOS is RHEL without logos and trademarks. So anything you get should be fine.

Personally, if you want to understand Linux inside and out, I'd do this: http://www.linuxfromscratch.org/

That is a good way to understand it but you need to have basic linux knowledge. And Read alot of the documentation provided

so what do you suggest?Should I go forward for this? Coz when i read their LFS that is Linux From Scratch they say in their homepage,"Linux From Scratch (LFS) is a project that provides you with step-by-step instructions for building your own customized Linux system entirely from source." whereas I want to learn and not build right away without knowing anythng!
Am I wrong?They also provide documentation to understand first and then build or directly build? Currently I am downloading CentOS 5.4(finished 1.5GB of download) and have some books on:
1] Definitive Guide to CentOS 5
2] Complete Idiot's Guide To Linux Programming
3] Red Hat Linux Networking and System Administration(Redhat Press)
4] A Practical Guide to Red Hat Linux 3rd Edition
5] Fedora Linux TOOLBOX 1000+ Commands for Fedora, CentOS, and Red Hat® Power Users.
I think these books are sufficient to have good command over linux and specially Red Hat as I want to do RHCE! right?

And can anyone exp-lain me what is this x86 and x86_64? they are just mirrors host right?? or got something do like 32 bit and 64 bit?? sorry for the stupid question,but am really confused!

1. "Linux From Scratch" is a project aimed at those already capable to work in the GNU/Linux commandline effectively on their own. There are many useful explanations in the LFS book, and you can learn a lot even from reading it, but it is not for the beginners. For example, they give complicated sed commands and count on reader's ability to understand what it does in term of literal text processing, so they only explain why it should be done.

2. Probably you should read 1 then 4 then 3 from your book list. At some point you could read some of the guides from TLDP - http://tldp.org/guides.html . Of course a few books and guides are not enough for mastering GNU/Linux.. I don't know what is needed for RHCE, though.

3. x86 is 32-bit. x86_64 is 64-bit.

I would not suggest you to dive in to LFS right now. Start off with RHEL or CentOS, whatever you can get and learn and get your certification. Once you are comfortable with Linux, you can go for LFS. Right now, CentOS is better for you to learn.

It never hurts to try it. I have build the temp system but haven't actually finished it. So give it a shot. You might not be successful but I'm sure you will learn a thing or 2