Mere Christianity, by C. S. Lewis
I've read this book several times, but this time I got it on Kindle for cheap. My own copy is an ancient paperback, and it was nice to get an ebook version with type that is easier to focus on. I enjoyed reading it very much. Isn't it funny how reading a book in a different edition or format can bring new details out? I have often felt like I was reading a whole new book when I got a new version of an old one.
Every time I read Mere Christianity I enjoy Lewis' insights. Of course that doesn't mean that I agree with him in every particular, but in the main there are few writers who can open a window into human nature the way he does.