I have just had my Kindle for 3 days and LOVE IT! The cheaper version does need a home wifi system, but the 3g version ($165) is online automatically in the US and 100 other countries. This is remarkable since you have no monthly note for service.
It does require some computer knowledge, but not much.
You must establish an account with the vendor where you buy ebooks. Every book that you get-unless it is free-will be on a creditcard, but I find the prices fair. And our local library will begin lending ebooks later in the year. Amazon will have a lending librabry, too. Eventually. I have a friend who also uses Kindle. We can borrow each others books!
I have no experience with other brands of ebook readers. I did research before buying Kindle.