Once you get your iPad, you must have been eager to put tons of e-book in your iPad. There are many sources where you can download unlimited e-book for your iPad. From iTunes, you need to pay per download. Some of the sites are offering reasonable fee for you to do unlimited download.

One of the site that I know and cost effective is myPadMedia. They charged only one time low payment with money back guaranteed.

Here are some info that I got from their site:

What type of eBooks can members get access to?

Members can download hundreds of types of eBooks, such as novels in a range of genres such as bestsellers, classics, mystery, thriller, crime, romance.
These aren’t books by authors you have never heard of, they are popular well-known books which are selling in your local bookstore or on the iTunes iBookstore.

Do I need a jailbroken or unlocked iPad?
No, you do not. myPadMedia works with ANY iPad. You do not need to modify your iPad or the operating system in any way. myPadMedia is designed to work on all iPads.

Is myPadMedia available to everyone around the world?
Yes, absolutely! No matter what country you are from, you can start using myPadMedia and gain access to thousands of multimedia files to your iPad right away.