I have a Kindle and my hub has a Nook Color..now if he had gotten me the Nook first I might have been sold, But I wouldn't give up my Kindle. The only downside is there is no backlighting. The Nook has that. But Booklights are easy so its really not an issue..just not built in.
I have over 400 books on my Kindle...very few did I pay alot for. I am reading the Revenge of the Radioactive Woman...very funny. But most are free. Type in "Public Domain" in the search and it will bring up more than you can imagine. And on Amazon there are always free books to download. Good Luck in your search! =)