I have a Kindle, with a keyboard. I don't use the keyboard very often, but it is useful. If you know the name of a book or an author you can search for it by typing in the details.
You can also use the Kindle to access the internet, although it's slow and, because it's only black and white, isn't really an ideal way to do this. Although I have used it to Twitter, in extremis, when bored and my mobile battery was running down too quickly!
If you get the one with 3G, which is the most expensive one, the advantage is that you can download books when you're out and about and don't necessarily have access to WiFi. For me this has been invaluable. I do a fair degree of travelling about for work, and don't always have the foresight to download a book before I go. And when DH and I went to Paris on the Eurostar, and the train broke down for 3 hours leaving us stranded, it meant that I could download another book to read.
Downloading a book is very easy. You select 'go to Kindle store' on the Kindle (there is a simple menu), and then tell it what book you want. Once you have told it to 'buy' the book is sent to your Kindle and will be there within less than a minute. (To be able to use a Kindle first have to set up an Amazon account).
When you look for books, there are lists of books by type - e.g. fiction/non-fiction, crime, horror - etc. There are also lists of free books, and a lot of classic titles are free. However, I have also found that even the ones you have to pay for are often significantly discounted. My recent purchases were around £2 each.
HTH!